Systemback suddenly changes the hostname and stops booting into desktop

from one day to the other my perfectly working systemback live usb (ubuntu 16.04) changes the hostname to "systemback" (instead of "life") and stops booting into kde

with ctrl+alt+f1 i can switch to a tty and then issue the command "startx" - the system can be used as usual then.. but this is creeping me out.. i makes absolutely no sense..

i don't know if this happens on live usb devices made directly through systemback though.

i use a specialized script to copy the original systemback usb drive to another usb drive... i create a fat32 partition for windows share,
then a fat32 partition for the system (the usb system partition is copied via rsync then)
and i use a special casper-rw partition and the boot parameter "persistent" in order to store all changes on the device.
at last i install syslinux on sdb2 (the system partition) to be able to support legacy bios

this works perfectly until - for no reason and without doing anything - the hostname is changed to systemback and kde stops loading.

this happens at least 1 time every month.. i use more than 80 usb devices like that with my students.

the interesting thing is: first i thought it has something to do with what i stored on the casper-rw partition... but even if i boot into the live system (without persistent) and casper-rw is not used at all the problem exists... something changed on the "systempartition" (which should never be touched at all)

do you have any idea whats happeing here ?
rsyncing the contents of the system partition from a working device and reinstalling the bootloader made the flashdrive work again..
only copying the initramfs and filesystem squashfs made the boot process freeze...

i did not try reinstalling syslinux only... (i have no test device right now.. but i will have one next month ;-( )