xubutu 18.04 screen locker can't be disabled

I recently upgraded from Xubuntu 16.04 to 18.04. In 16.04 I set the XFCE power manager to sleep after about an hour and never saw a locked screen.

Now in 18.04 the screen is locked after an hour at idle.

I have disabled the screen locker in Session and Startup and unchecked the Lock screen in Power Manager.

What else can I do?

Linux gaines 4.15.0-34-generic #37-Ubuntu SMP Mon Aug 27 15:21:48 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
description: Desktop Computer
    product: Vostro 470 (To be filled by O.E.M.)
    vendor: Dell Inc.
    serial: BMKMTW1
    width: 64 bits
    capabilities: smbios-2.7 dmi-2.7 smp vsyscall32
    configuration: boot=normal chassis=desktop family=To be filled by O.E.M. sku=To be filled by O.E.M. uuid=44454C4C-4D00-104B-804D-C2C04F545731
  *-core
       description: Motherboard
       product: 0NW73C
       vendor: Dell Inc.
       physical id: 0
       version: A01
       serial: ..CN7220031O003S.
       slot: To be filled by O.E.M.
     *-firmware
          description: BIOS
          vendor: Dell Inc.
          physical id: 1
          version: A10
          date: 10/19/2012
          size: 64KiB
          capacity: 4032KiB