It only happens during vet trials specifically, I literally do everything else in the game just fine including the normal versions of trials. I meet or exceed the recommended requirements to run the game so I really don't know what to do.
Strange if you're able to enter normal trials without issue.
Then you have to narrow down what's different to a normal / vet trial and the only thing I can think of is that it could possibly be a conflict in an addon that enables itself for vet encounters. Specifically certain boss abilities you wouldn't otherwise encounter on normal.
It could be Raidnotifer It's been an issue for some time but it really hasn't been an issue as I haven't really had a need to do vet trials before. now that I've though about it, the crashes on vet trials but not all the time as when I was doing vSO for the first time in a while (probably since installing Raidnotifer) it crashed quite a bit (at least 3-5 times) but the next time I did it it didn't happen at all