Macrium may have some sort of incompatibility with some newer Dell XPS systems.  If scheduled, they will wake the system from sleep, complete the backup and begin shutdown.  If they are not sleeping, the issue does not occur.

The shutdown will not completely execute.  The systems remains powered.  If a keyboard key is pressed, the system then powers off.  Any suggestions?  This bug is present on several XPS systems from different households, models 8920,8930,8940 (several generations).

The systems have the PE, the latest Macrium version (currently 8.0.6635), the latest Windows 11 versions (the issue was present with Win10 and has been a problem for a year or more) and some experience it out of the box.  Motherboard, storage and other firmware and drivers are updated.  Any assistance is appreciated.

Would any of the diagnostic switches for POWERCFG.EXE be useful to you diagnosing the cause?
I'm thinking there may be some clues in /sleepstudy /systempowerreport or /systemsleepdiagnostics
Command-line reference for powercfg here 
I've managed to track down the culprit with odd sleep/wake issues in the past using the tools provided by powercfg, though not always.

What version of Windows are you running?  I've had a couple cases of Win11 not sleeping even though powercfg -requests showed nothing keeping it from sleeping.  (Very inconsistent.  Any time I try to catch the failure the computer goes to sleep without problem.)