Failed saving grub configuration

I have recently set up MX18 and Ubuntu MATE on a second disk on my pc (The first disk is windows 10). I have configured the machine to normally boot straight into windows and only to display the grub menu for the 2 linux systems only when I interrupt the boot sequence to get the bios (ie the grub was installed on sdb only)
I tried to change the order of the grub entries by putting memtest to the end and got "Failed saving grub configuration" message saying:
failed running 'grub-mkconfig -o " /boot/grub/grub.cfg"
...
Syntax errors are detected in generated GRUB config file

I am afraid I'm a newbie and don't know how to check for sytax errors, but have attached the content of of grub.cfg.new file as instructed

#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
  set have_grubenv=true
  load_env
fi
if [ "${next_entry}" ] ; then
   set default="${next_entry}"
   set next_entry=
   save_env next_entry
   set boot_once=true
else
   set default="0"
fi

if [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
else
  menuentry_id_option=""
fi

export menuentry_id_option

if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}
function load_video {
  if [ x$feature_all_video_module = xy ]; then
    insmod all_video
  else
    insmod efi_gop
    insmod efi_uga
    insmod ieee1275_fb
    insmod vbe
    insmod vga
    insmod video_bochs
    insmod video_cirrus
  fi
}

if [ x$feature_default_font_path = xy ] ; then
   font=unicode
else
insmod part_gpt
insmod ext2
set root='hd1,gpt6'
if [ x$feature_platform_search_hint = xy ]; then
  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
else
  search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
fi
    font="/usr/share/grub/unicode.pf2"
fi

if loadfont $font ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  set locale_dir=$prefix/locale
  set lang=en_US
  insmod gettext
fi
terminal_output gfxterm
if [ "${recordfail}" = 1 ] ; then
  set timeout=30
else
  if [ x$feature_timeout_style = xy ] ; then
    set timeout_style=menu
    set timeout=5
  # Fallback normal timeout code in case the timeout_style feature is
  # unavailable.
  else
    set timeout=5
  fi
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
insmod part_gpt
insmod ext2
set root='hd1,gpt6'
if [ x$feature_platform_search_hint = xy ]; then
  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
else
  search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
fi
insmod png
if background_image /usr/share/backgrounds/MXLinux/grub/linen-gradientblu-grub.png; then
  set color_normal=light-gray/black
  set color_highlight=magenta/black
else
  set menu_color_normal=cyan/blue
  set menu_color_highlight=white/blue
fi
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
 set gfxpayload="${1}"
}
set linux_gfx_mode=
export linux_gfx_mode
menuentry 'MX 18.3 Continuum' --class mx --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-1afb0e21-a3ab-46c8-bc6b-5621d0adad1a' {
 load_video
 insmod gzio
 if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
 insmod part_gpt
 insmod ext2
 set root='hd1,gpt6'
 if [ x$feature_platform_search_hint = xy ]; then
   search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
 else
   search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
 fi
 echo 'Loading Linux 4.19.0-5-amd64 ...'
 linux /boot/vmlinuz-4.19.0-5-amd64 root=UUID=1afb0e21-a3ab-46c8-bc6b-5621d0adad1a ro quiet splash
 echo 'Loading initial ramdisk ...'
 initrd /boot/initrd.img-4.19.0-5-amd64
}
submenu 'Advanced options for MX 18.3 Continuum' $menuentry_id_option 'gnulinux-advanced-1afb0e21-a3ab-46c8-bc6b-5621d0adad1a' {
 menuentry 'MX 18.3 Continuum, with Linux 4.19.0-5-amd64' --class mx --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-4.19.0-5-amd64-advanced-1afb0e21-a3ab-46c8-bc6b-5621d0adad1a' {
  load_video
  insmod gzio
  if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt6'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
  else
    search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
  fi
  echo 'Loading Linux 4.19.0-5-amd64 ...'
  linux /boot/vmlinuz-4.19.0-5-amd64 root=UUID=1afb0e21-a3ab-46c8-bc6b-5621d0adad1a ro quiet splash
  echo 'Loading initial ramdisk ...'
  initrd /boot/initrd.img-4.19.0-5-amd64
 }
 menuentry 'MX 18.3 Continuum, with Linux 4.19.0-5-amd64 (systemd)' --class mx --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-4.19.0-5-amd64-init-systemd-1afb0e21-a3ab-46c8-bc6b-5621d0adad1a' {
  load_video
  insmod gzio
  if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt6'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
  else
    search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
  fi
  echo 'Loading Linux 4.19.0-5-amd64 ...'
  linux /boot/vmlinuz-4.19.0-5-amd64 root=UUID=1afb0e21-a3ab-46c8-bc6b-5621d0adad1a ro quiet splash init=/lib/systemd/systemd
  echo 'Loading initial ramdisk ...'
  initrd /boot/initrd.img-4.19.0-5-amd64
 }
}

### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###

### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/30_os-prober_proxy ###

menuentry "Ubuntu 18.04.2 LTS (18.04) (on /dev/sdb5)" --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-simple-8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
 insmod part_gpt
 insmod ext2
 set root='hd1,gpt5'
 if [ x$feature_platform_search_hint = xy ]; then
   search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
 else
   search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
 fi
 linux /boot/vmlinuz-4.18.0-25-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro quiet splash $vt_handoff
 initrd /boot/initrd.img-4.18.0-25-generic
}
### END /etc/grub.d/30_os-prober_proxy ###

### BEGIN /etc/grub.d/31_memtest86+_proxy ###

if [ "${grub_platform}" == "pc" ]; then

fi
### END /etc/grub.d/31_memtest86+_proxy ###

### BEGIN /etc/grub.d/32_os-prober_proxy ###
submenu "Advanced options for Ubuntu 18.04.2 LTS (18.04) (on /dev/sdb5)"{
menuentry "Ubuntu (on /dev/sdb5)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.18.0-25-generic--8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt5'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  else
    search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  fi
  linux /boot/vmlinuz-4.18.0-25-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro quiet splash $vt_handoff
  initrd /boot/initrd.img-4.18.0-25-generic
}
menuentry "Ubuntu, with Linux 4.18.0-25-generic (on /dev/sdb5)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.18.0-25-generic--8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt5'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  else
    search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  fi
  linux /boot/vmlinuz-4.18.0-25-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro quiet splash $vt_handoff
  initrd /boot/initrd.img-4.18.0-25-generic
}
menuentry "Ubuntu, with Linux 4.18.0-25-generic (recovery mode) (on /dev/sdb5)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.18.0-25-generic-root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro recovery nomodeset-8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt5'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  else
    search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  fi
  linux /boot/vmlinuz-4.18.0-25-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro recovery nomodeset
  initrd /boot/initrd.img-4.18.0-25-generic
}
menuentry "Ubuntu, with Linux 4.18.0-15-generic (on /dev/sdb5)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.18.0-15-generic--8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt5'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  else
    search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  fi
  linux /boot/vmlinuz-4.18.0-15-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro quiet splash $vt_handoff
  initrd /boot/initrd.img-4.18.0-15-generic
}
menuentry "Ubuntu, with Linux 4.18.0-15-generic (recovery mode) (on /dev/sdb5)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.18.0-15-generic-root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro recovery nomodeset-8237c9f7-9fbc-45ed-8467-cd5c0454d7d1' {
  insmod part_gpt
  insmod ext2
  set root='hd1,gpt5'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt5 --hint-efi=hd1,gpt5 --hint-baremetal=ahci1,gpt5 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  else
    search --no-floppy --fs-uuid --set=root 8237c9f7-9fbc-45ed-8467-cd5c0454d7d1
  fi
  linux /boot/vmlinuz-4.18.0-15-generic root=UUID=8237c9f7-9fbc-45ed-8467-cd5c0454d7d1 ro recovery nomodeset
  initrd /boot/initrd.img-4.18.0-15-generic
}
}
### END /etc/grub.d/32_os-prober_proxy ###

### BEGIN /etc/grub.d/33_memtest86+_proxy ###
menuentry "Memory test (memtest86+)" {
 insmod part_gpt
 insmod ext2
 set root='hd1,gpt6'
 if [ x$feature_platform_search_hint = xy ]; then
   search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
 else
   search --no-floppy --fs-uuid --set=root 1afb0e21-a3ab-46c8-bc6b-5621d0adad1a
 fi
 linux16 /boot/memtest86+.bin
}
### END /etc/grub.d/33_memtest86+_proxy ###

### BEGIN /etc/grub.d/34_uefi-firmware ###
### END /etc/grub.d/34_uefi-firmware ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f ${config_directory}/custom.cfg ]; then
  source ${config_directory}/custom.cfg
elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

Please can you advise?

Many thanks,
Tony