Comment 18 for bug 1779063

It seems one of the RAM modules in that machine degraded over time - while memtest86 found no problems in the past, now errors are discovered within seconds.

It's unclear when the module became faulty, but it's quite plausible that the observed kernel panics were caused by this and that there's no actual software bug involved.

I'll replace the system RAM and revert back to the normal Ubuntu kernel. I think this issue can be closed - if the same symptoms reassert themselves, things can be revisited.