Hi,
Unfortunately I decided it is best to start my project anew rather than try to fix all the bugs. I first started this project with 4.6 so I thought it was a good time to remake it. I tried looking for solutions but it was really long and tedious, having to step through engine code.
In the beginning the error was coming from spawning my bots. Then as I described in my original post, when I tried editing my Game Mode BP. After a while the crashes resolved themselves despite me not doing anything. The last issue I was able to find was caused by the function Load Game (sorry for not having the exact name) from UGameplayStatics. The serialize at the end was causing a crash as well. This is easily fixed by deleting your save game file and letting the engine create a new one. I guess working with 4.7 save file causes problems.