[TeMPOraL]

I'm guessing it's the HDD that's failing. Had such mysterious failures with my NVR (the Cloud Key thingie) from UniFi. Turns out, HDDs don't like operating in 60+ degree Celsius heat all the time - but SSDs don't mind, so fortunately the fix was just to swap the drive for a solid state one.

[dgacmu]

I think it was the DRAM on mine, oddly. It already uses an nvme ssd. Could have been the CPU, of course - the error was manifesting as memory corruption but that could well have been happening during read or write.