Schedul2.exe crashes during bootup, no backups possible! (build 12.5.8690)

System: Win 10 pro 64-bit, running AB 12.5 with both Management Server and Agent on same device.

Error/Issue: Updated to build 8690 from build 7970 on Dec 17, 2017. Update successfully completed without error message.

Now, every time I start the computer, schedul2.exe crashes with this message:

Name der fehlerhaften Anwendung: schedul2.exe, Version: 8.0.1.8430, Zeitstempel: 0x5a2f9bc1
Name des fehlerhaften Moduls: schedul2.exe, Version: 8.0.1.8430, Zeitstempel: 0x5a2f9bc1
Ausnahmecode: 0xc0000005
Fehleroffset: 0x0000000000033627
ID des fehlerhaften Prozesses: 0x42e0
Startzeit der fehlerhaften Anwendung: 0x01d378ec92095724
Pfad der fehlerhaften Anwendung: C:\Program Files (x86)\Common Files\Acronis\Schedule2\schedul2.exe
Pfad des fehlerhaften Moduls: C:\Program Files (x86)\Common Files\Acronis\Schedule2\schedul2.exe
Berichtskennung: fbe14107-024c-45bb-b895-ca454201b609
Vollständiger Name des fehlerhaften Pakets:
Anwendungs-ID, die relativ zum fehlerhaften Paket ist:
 

The schedul2 service apparently repairs itself after a certain time but then crashes again after a few hours or when waking up from energy saving mode. No backups possible because monitor says "internal error" in lower right corner.

Update. The same scenario is true for a client without AMS, repair function does not help, uninstallation and re-installation does not work either. Antivirus whitelisting on/off makes no difference.

I cannot use the product! Urgent help would be appreciated,

Steve