do you have a UPS (battery backup) connected to the system?
can you monitor the power consumption when this is happening?
what else is connected to your system? what occupies USB, PCIe, SATA, etc.
FileVault enabled or disabled?
APFS or HFS+ system drive?
SIP enabled or disabled?
Gatekeeper enabled or disabled?
It likely is not tied to Adobe if happening at other times, but worth mentioning that the GPU is often engaged more frequently in Premiere than AE, depending on which renderer option you are using, if Dynamic Link is involved at all, and your playback resolution. Clearing Adobe from all startup MAY help and would recommend.
If this is a PSU issue, I've had some short-term luck in the past on a client machine by limiting the unnecessary devices connected to the machine. Basically can get a few weeks of work done, if you're waiting for a replacement part.
There is another member on this forum that recently had his machine die with the GTX 1080 Ti. Believe is/was on a 4,1>5,1. Maybe worth seeing if
h9826790 has any insight?
Let's talk about the OP's case first. I tend to believe it's a PSU failure. If CPU / CPU tray / logic board / RAM / HDD.... failing, should not be always instantaneous shutdown. Most likely will have some crash / KP / beachball / instability as well.
About my own case. My cMP was very normal until few weeks ago. The ethernet card seems suddenly become unstable (simply no connection regardless I boot to Windows / macOS, but few more reboot / PRAM reset may fix it. And once it work, it will work until next boot). I didn't realise it may be a sign of logic board failing.
Until few days ago, I decided to reboot to Windows. Restart hang with black screen (power ON, fans ON, no chirm, USB mouse ON, optical output OFF, USB keyboard OFF, can't get into firmware restoration mode, can't perform PRAM reset....) and the cMP simply dead.
Lucky enough, I found a very good condition (ex university use) dual processor 4,1 yesterday for $450. Two weeks warranty from the seller. Local store, no shipping cost. Immediately available. That help to fulfil my wife's request (fix the cMP ASAP before I start to dive into the Hackintosh)
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Anyway, with this "new" cMP, I can confirm that my cMP's logic board is dead. PSU is good. Since the Pixlas mod has been done. Pretty sure not because of the 1080Ti's power draw. At least not an instant direct kill.
I over stress the mini 6pins for many years already (I ran dual HD7950 with mini 6pin only). Of course it can be the cause of pre-mature failure. However, my cMP run 24/7 since 2009. And often under 100% load. In the first few years, I have no idea that I should do some regular maintenance. The cMP actually ran hot for quite a few years initially (Hong Kong is very dusty, the heatsink / PSU will cover by dust in just few weeks). That may shorten the life span as well.
Anyway, 9 years of 24/7 work with often 100% loading. I won't call it "pre-mature" failure. May be it's really about time.
Let's see how long my 2nd logic board can do. I re-use the Pixlas modded old PSU, and old upgraded CPU tray now. I assume If this logic board hasn't die within weeks, then my Pixlas mod was good, and that's not the cause of cMP's death.
When I replace the logic board (because my own cMP's case still in better condition. And I have to remove the CPU cage for wifi ac / BT 4.2 card installation anyway. But the new cMP's internal parts are in much much better conditions), I found that even though the front side of the logic board is very clean. The back side still has quite a bit of dust. Not sure if that contribute to the failure.
