MacPro (late 2013) Audio Stuttering

Bought used MacPro several years ago from OWC with their high end 1TB internal Aura Pro X SSD that was only just then supported by macOS. Audio from the analog output starts stuttering within a few days of a reboot. User interface gets a bit jerky too. Has been doing this from the start, I should have returned to OWC.

When this problem occurs the machine will not shut down cleanly. It eventually does, maybe 30 minutes? I don't sit around and wait for it. On reboot message appears stating machine crashed, not shut down properly, or something but "would you like to report to Apple?" I do, not that it makes any difference now over multiple OS updates over the years.

I have tried reinstalling OS. Have tried a wipe and install from Time Machine. Have not tried a complete wipe and reformat, fresh OS, then Migration Assistant. Might just try that so as to get case-sensitive APFS.

Currently has the 2nd update of 10.14.6.

How to procede?