Topic: Debug/fix frequent 3-5 sec AV sync delay, then recovery of video?

I use MPC-HC (LAV, AviSynth+ 3.7.2, AviSynthFilter, CUVID hwdec) often for MKV playback for hours.  Watching a TV series episode by episode, while doing something else too.  The sound works fine the whole time, but 2-3 times a day (at least) the video will just stop updating for 3-5 seconds.  It eventually catches up, or my whole system reboots.

I can't find a record of these anywhere.  No logs mention a problem, even a recovered problem.  I mean they won't unless I crash/reboot.  And then it'll just tell me a GPU related part of software failed (which might mean RAM too).

I have 2 of the same video card.  I've tried with one card, and with 2 card installed (SLI turned off, since it doesn't improve results on my 1080 ti system, and I don't play high end games anymore).  Pretty sure I've even tried each card separately, just in case one was unstable.

Only things that seem to impact results are other settings that cause crashes.  My system won't run at XMP RAM speeds by default.  And when I enable it I get a lot more crashes.  If I also adjust from "normal" to "enhanced stability" (versus enhanced performance) it crashes less often, but I still see frequent pauses daily until it recovers.

Without the "enhanced stability" change (at normal) I can get passing RAM test results from memtest86+, but it needs "disable fast boot" under memory options (versus automatic or enable fast boot... this "trains the memory" more carefully at boot).

So in closing... does anyone else see this regularly?  Intel i7-4790k CPU, DDR3 RAM 1600MHz C9, z97 motherboard, 1080 ti x 2 video.  And is there a way I can fix it (different BIOS setting?) or report where the issue(s) are (what software is doing or seeing when it happens)?

I'm running at stock CPU speeds too.  Typically this CPU is stable with an overclock, but things get worse if I try to.  And I can cause enough stress with Prime95 to crash any overclock.  My motherboard was overvolting my CPU for about 3 years until I figured out why (auto vs. normal BIOS setting chose 1.4V instead of 1.2V).