TLDR: It’s probably an issue with D2R and your NVIDA GPU. Some people get it, some don’t. Fortitude seems to be a cause of many of these issues. A friend of mine has experienced this and I looked into it for him. There are several posts about this issue in Technical Difficulties. Here is a link to one of them:
Here is a link to another one, although it discusses crashes, the two issues are often connected:
I would suggest checking them out or other posts like it.