I think this has happened twice now, but the first time was months ago. Both times it was definitely on a Synedrion map, and the most recent time it was while taking control of an infiltrator unit - I think the first time was as well, but I can’t swear to it.
So this time, I accidentally landed one of my heavies doing a jet jump right next to one of Synedrion’s infiltrator guys - I couldn’t see the infiltrator when I executed the move. For info, this was on a roof. Everything was ok until I selected the infiltrator, but when I did, the whole control system bugged out and started acting erratically - icons not doing what they’re supposed to, etc. I figured the temporary fix was to hit escape (to the menu), then select another unit on the map (tab didn’t work). However, when I selected the infiltrator, the same thing happened. This went on for a while until I completely lost control of the game, and even Windows - CTRL-ALT-DEL didn’t even work, nor ALT-TAB, nor WINDOWS-TAB. I had to do a hard shut down. Forgot to try ALT-F4.
I reloaded, started the tactical mission again from the auto save, and this time intentionally took control of the same guy, and it happened again, but not as badly - I saved before the PC locked up. I then restarted my machine once more to test, and reloaded my manual save, and the bug was proved to be baked into the save file.