Wow interesting... another AMD case again.
Look like you found the root of issue triggered Event ID 161 is a "volmgr" (Volume Manager) error in Windows that indicates a failure to create a memory dump file. Volmgr is Volume Manager Driver file managed drive data storage.
The event ID 161 Volmgr is logged when a BSOD error occurs on Windows 11. To fix it, update outdated drivers or run an SFC scan.
windowsreport.com
Event ID 161 probably caused by bugged BIOS or outdated drivers or third party apps you installed.
Make sure you update latest BIOS to version FGh released 12 August 2025.
https://www.driveridentifier.com/ download Driver Identifier to scan your device drivers to find outdated drivers then download and update latest drivers.
Maybe KB5063878 conflicted with third party apps that triggered Event ID 161.
I think you should report on Feedback Hub and submit your diagnostic data, your data probably will help Microsoft engineers finally identify mystery issue caused SSD disappeared with KB5063878 update.