I made no changes before the update.
After the update, I experienced this error, so I updated my GPU driver immediately.
I then tried Thok Ast Thok (Extreme) and didn't experience the issue upon returning to Mist from the instance. I proceeded to try Thornmarsh (Hard), on accident, so I used the Leave option to exit without any issues. Then I tried Thornmarsh (Extreme), completed it, exited it, and then the error happened again like before.