@ Eggbert
I have no idea what Auslogic Reg Defrag is doing, but I use RegSeeker by HoverDesk and avast has no issue with that.

My only guess is that it is trying to remove an avast related registry entry, then it wouldn’t matter if you had the shields disabled, the problem could lie with the avast self-defence module, AvastUI > Settings > Troubleshooting. Turning it of whist you do the defrag might work.

Unfortunately there is insufficient information to say for sure.

Since avast doesn’t run in safe mode, there can’t really be an interaction with Auslogic Reg Defrag. But then the question is, is Auslogic Reg Defrag able to run in safe mode either ?