Civilization 6 Unhandled Exception Error: EXCEPTION_ACCESS_VIOLATION 0xffffffff (Fixed)

[Das Capitolin]

My friends and I wanted to play a multiplayer game of Civilization VI together, which we had not done in over two years. One of the players suffered desync nearly every turn, and his game would crash every few turns with this error:

Unhandled Exception
Code: EXCEPTION_ACCESS_VIOLATION
Error reading address 0xffffffff

Call Stack
-----------------------------------------------------
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
??? ! ??? ???, line 0
​

The game logs revealed nothing more than the above error. In researching this issue, we found many different suggestions: from clearing the cache, to updating graphics drivers, to reinstalling the game. All of these were tried, but in the end the culprit was mods.

To troubleshoot, we disabled all community mods and then we played 30+ turns of Gathering Storm. Flawless. Not one issue. So then we systematically enabled one mod, and started a new game. 30 or so turns played each time, with no issues experienced. Previously we could not make it more that five turns without a crash.
Although the testing could have continued, we tested our most important mods and decided to begin an actual playable game. So far, we've enjoyed 100+ turns without desynchronization or game crashing.

For reference, all of the community mods we use have worked fine in single-player games. I have personally played with about twenty of them enabled at once. However, as we selectively added one at a time, we were happy with the handful tested and the group wanted to move on to playing. There were still several untested, and the offending mod(s) likely reside in this group. Your mileage may vary, but this is how we solved the repeated Civ 6 Unhandled Exception Error.

 

[Das Capitolin]

PS: My friend thought for sure it would be one of the mods I created, because we were all playing with my recently updated Warmonger Nuclear Domination mod. It's a good thing I did lots of testing before release (which is not always the case - sorry!), because it passed with flying colors. I'm glad, too, because it did exactly what it was supposed to, and we were getting attacked by everyone after our second era.