Scheduler Service Initialize / AfwScheduler.exe APPCRASH Windows Event
Scheduler is not running anymore. Two weeks ago we applied 9ARD183777-020 Qualified Security updates ,6.1 RU1 / RU2 and disabled several windows services as described in 3BSE080520-610_en_System_800xA_Security_Deployment_Guide.pdf AfwScheduler.exe crashes as logged by system event.
Try catching a crash dump by turning on Dump On Exception in the classic Configuration Wizard (press & hold ALT-SHIFT to unlock this setting) then check if any .dmp files become generated below C:\ProgramData\ABB\Process Portal A\Crash. Then file a support case with your regional ABB support center and hand over the dumps, compressed.
I recommend creating (cold) drive image backups prior installing QSU to be able to fall back.
The hardening policies should be able to be temporarily revoked or moved out of scope for struck machines (+GPUPDATE.EXE /FORCE) as a test to see if they have caused any harm.