Thanks for the confirmation, this is exactly what I needed to know.
The fact that the 3440x1440 resolution doesn't appear in the initial list validates the cause of the problem. The system wasn't correctly recognizing it, which is why the game couldn't revert to your original resolution.
The fix I implemented was made to handle this situation. Even if the resolution isn't listed, the game should now be able to identify and recover it.
As I said before, the fix will be in the next update. 👍
All the best!