Oh I edited my last comment, but it seems that it didnt save…My bad.
I have figured out what you just said earlier before you post this, and figured out why the crash occurs after restarting the game.
If you can help me in this I’d be very glad :
So My game uses 2 characters, one character per player, I use the defaultly spawned character for player0 and i spawn another character (with a controller) for player1 to use. When I restart the game, I get an additional player spawned (having 3 players), I dont know why this happens 
I even tried to destroy all actors before restarting, but didnt work, I still get 3 characters.
Ill dig more into this and see, Anyway Thanks for your help 
EDIT:
Okay I figured it out, when I create a player controller using UGameplayStatistics::CreatePlayer(), the player persists when restarting level, so I had to add an additional check whether i already have player1 or should i create one.