So yes is this known bug or is my old pc just acting up again.
As you will see here the main game menu load function likes to crash with this error when i have 7 under slots filled with save games and i try to go from 1 to 7 in the lower number or from 7 to 1.
But when i am in the game and select the save load menu from there it doesn't crash. Then it remembers where i loaded saved and when i move 7 slots only in one direction full of saves this error pops up:

Edit: seems like there was an update in 2020 and i played this game with version 2018 probably.
Maybe that is why the bug existed. Gonna update the game
Edit2: the updated game doesn't crash anymore with the problem mentioned above.