I queued for a game in casual mode and then the map etc. loads, but the second I load into the match my game instantly crashes. (This problem doesn’t occur when loading into a community server.)

So now I uninstalled mastercomfig according to their guide and in this process also removed the custom hud.

So now I did some testing (without any of those modifications to the game):

I play TF2 in windows mode and based on my small(!) sample size this my conclusion of the test:

• If I open TF2 and don’t drag the TF2 window elsewhere, it seems I can queue for casual without crashing after loading (the map etc).
• BUT If I drag the window to my second screen and then try to queue for casual, the game crashes instantly after loading.

This is so frustrating. But it seems like a pretty rare problem, looking at the TF2 subreddit and the steam discussions.