In the American mission before Natural Born Heroes, Payback I think it is called, you can quickly and very easily rush the Russian bases and destroy their depots. However, if you somehow managed to get everyone killed and then yourself after the 21 min mark, Harris will begin talking to you without you responding back. Now, in natural born heroes, you defend your base and eventually your squad comes popping up to save the day, but no John. People continue talking to you like you are there, but you're not. You can complete the game real easily by rushing the base and just slaughtering as fast as you can with what you have, even less, and the game ends without John. Then the next mission you need to get to the base that has the captured Siberite mine, but you cannot without John's presence, making the game forever at a standstill.
Basically, I found the same problem again but caused it a mission sooner. Also, I posted this in my last topic but I thought it would be worth saying again because it doesn't deserve its own topic, but John acts like Joan died at Gamma based in Natural Born Heroes, even if she actually died on the mission From the Future with Love.
I hope you guys don't mind me tearing the game apart and finding mediocre game bugs, since I know you guys are primarily interested in multiplayer.
edit: forgot to mention this is 1.12.7