Hi, thanks for the response.
CursorFX now indeed lets me register it again, but I still have to do it virtually every morning.
Fences will now sometimes out of the blue pop up a small screen saying it can't find the activation, and I have to re-enter the code.
I am using Acronis True Image 2021 (it's a new version) that includes protection against malware - I will turn off protection for a day and see what happens.
I am also running Avast antivirus or whatever it's called now, that I am NOT willing to turn off. But I have been running that for years, and I do not think it is causing the problem.
Neither of these apps shows the license files quarantined, while other files are not deleted without warning, even if they're flagged as suspicious or outright malware - those go to a quarantine folder.
As far as I know I have no other malware protection apps installed.
BTW I just noted one of the license files has again disappeared. The app does continue to run normally though.
ETA: for now, I have added the license files as exceptions for both Avast and Acronis. I will see how that goes.