I ran it again today. Initial CPU temp 32C. I began capturing immediately. Same issue, after about 10 frames, no frames come in anymore. Temp goes up to max 55C.
I also tried the ASI385. It also fails after a while. I think after maybe 30 frames or so.
I even tried it without Fits previews. This does not make a difference at all.
I also run Armbian 5.85 Stable
The NanoPi keeps functioning without freezing, kstarts keeps running, no problems there either.