[Schottlandru]

Thanks!
Onedrive is disabled, but there is a mirror service that I am still trying to deactivate. It is somehow protected enough easily disable to be our services, maybe I need to do a registry hack.
Turbo boost disabled, I tried c States and hyperthreading, no difference. I disable turbo and check for throttling via throttlestop.
LatencyMon is smooth, all green. But good point, I'll see if I catch anything when when this event log ID kicks in.
The thing is, Audio isn't affected, playback is smooth. It is a purely graphic issue.

Processor Affinity doesn't change or target this specific issue, minor audio improvements noticable though in full sessions.

There seems to be sth targeting a specific CPU core, that goes up to 60% or so constantly after some time. The rest are at under 10%, so all in all it doesn't register. If anybody knows how to analyse threads or processes on individual cores, I'd be happy to hear. The core number changes with every reboot, so I don't think it is is a hardware issue.