Chess Engine crashing for recursion search with depth = 4

Hi, im currently making a chess engine in Godot, using C++, rn im testing the speed of searching all moves posible. I made a version in which each time i did a move i copied all the variables (in a struct called GameState) and when i undo the move i just set the current state to the prevous one (saved in a variable GameSTate* prev_state). But i saw that wasnt very fast, so i searched what i could improve, castling checking, implementing magic bitboard, and move undoing. So instead of coping the whole state, i just undo the moves in place, with the same varibales and just encapsulate some variables like castling_rights and en_passant_square, in GameState, this make it around 2x-1.5x faster, but now for some reason when i try to search with a depth = 4 it just crashes. If someone thinks that can help me, or maybe need some fragments of the code he can text me in private. Thanks.