Does anybody here know the relationship between Nvidia DGX1 and P3D? I have gotten a few P3D error with 3 choices cancel/continue/exit. I don't see LM on the list of partners either.

There have been numerous discussions about this both here, FSLabs forums, other FS forums, and generally over internet. It happens in other games too, seems to be mostly Nvidia problem, but also AMD. Crashes also happened before, but we weren't aware that it was a DXGI problem (it's actually just a simple GPU crash, with Windows 7/8/10 built in recovery), and since a specific P3D version, LM introduced a window (what you described) that shows you the DXGI crash - it's nothing else but a message to the user about a problem that exists longer.

Causes are unknown really,  numerous speculations are very wide, there are lots of fixes one can try, best just search the net and read some discussions around. Through some of the fixes one can avoid it only really, and if you are lucky, you don't have them at all or are able to avoid them mostly. For each computer there seems to be another solution or whatever works.