You might benefit from the following if you haven’t tried it already:
-Diablo IV has run out of memory - #103 by DTMAce-1687
Have any of you looked at your fenris logs to see if you can locate the start of the error when it crashes?
You can run out of virtual memory. If you are monitoring it, make sure to monitor the “Committed” memory section under the main memory performance page in Task Manager.
One of the reasons I post about this in various threads is because I had experienced it back in January. In my case, it was upgrading to a 4080S from a 3070Ti that caused it. Back then I was not running a swap file at all, as I have notoriously never used swap files for years. But when I upgraded the card, I started getting out of memory errors. Turns out that having double the memory on the GPU caused the system to try to allocate more virtual memory. So I had to enable the swap file.