Hi there!
... after two weeks of trying and trying I just disabled the AntiVir Guard. And what can I tell.. no more stuttering whatsoever. Now I just have to ask myself if I can live with a media pc without virus protection.. But I think.. yes I can.
I hope this will help some frustrated stutter victims out there.
billiloumez
It's a known issue that you should not allow AV scanning of your Timeshift & Recording folders. So you might want to try just adding these folders as exceptions in your Antivirus. Sounds like you are using Avira so you can do this (Goto: Configure -> [Expert mode] -> Scanner -> Scan -> Exception. Repeat for Guard).
Other free Antivirus solutions may not allow this (e.g. Grisoft AVG) - in which case you should change to one that does!