ssd Drive Self Tests get corrupted -- motherboard problem?

[Humphrey_vpp]

Hi,

I bought a refurbished Elitedesk 800 G2 SSF last year and installed Linux/Ubuntu and I am quite happy with it.  Later, I installed a 120GB Intel ssd without any problems and, later still, I installed a 480GB Kingston ssd and I was quite happy with the result.

But then I noticed that the system would sometimes take a while to shutdown; the OS would close down and the screen would go black, but the power light would stay on and the cpu fan would keep spinning.  And when it once took more than a minute, I forced a shutdown by holding down the power button, which I think might have been a bad decision, because at next boot up there was a string of error messages complaining about orphaned nodes, which the OS fixed.  But things got worse in the sense that the Short Drive Self Test became unavailable and then the ssd wouldn't even boot up anymore. 

I approached Kingston support and with their help established that the ssd was essentially okay and unlikely to have been the cause of the problems.  Indeed, I am now running the Intel ssd and the PC is still sometimes taking unreasonably long to shutdown.  Anyway, on Kingston support's suggestion I did a "secure erase", updated the firmware (while in a caddy connected to my Windows10 laptop) and reinstalled the OS, but the problems remained: delayed shutdown and corruption of the ssd, so I turned the ssd in for warranty and purchased another ssd (same brand: Kingston).  But the new ssd suffered the same corruption of both Drive Self Tests.

Now,I am told that the cause of the problems is most likely a faulty motherboard, but I am loath to trash the PC, because it is sufficient for my needs and I like it.  So, unless somebody has an answer to this problem, I want to replace the motherboard.  Unfortunately, a HP replacement is no longer available, so my question is: would anybody know whether I can replace the motherboard with a non-HP one?