Just to know if anybody has had a similar experience:
I open a RAW file in LR
I do some adjustments there and then open it in PS as TIF.
I do there some adjustments, layers, masks etc.
In a copy of Background I apply Topaz AI as a filter.
Takes some time but that's not the issue.
After that I flatten the image and save (AI Topaz is closed)
Go back to LR
I repeat this procedure
with different files.
Gradually my PC slows down ...and down..
I'm wondering if that has anything to do with Topaz.
I'm not pointing fingers at it, it's just that I don't have any clue
If I restart my PC everything is OK again