Hi @andSmv
thanks for your tips - I have been trying some time and did not have any luck with it. However one time the whole xcp-ng host went down and rebooted and then I got an entry in the Supermicro IPMI with an uncorrectable ECC memory error. Memtest x86 did not report any faults but after changing that particular DIMM module the reboots and triple faults just stopped. So I think it is safe to assume that these error occured because of a hardware failure and the VM triple faulted because of that memory segment not being available.
I just wanted to report back for anyone encountering this. Thank you for your help.