Another update: The problem was actually that I was not using stable sort when I scored the moves.
History moves is actually working good!

Update: I checked other source codes and tried out examples from a tutorial: Well, as it turns out, history moves is working with the example from the tutorial, but it fails greatly in my mate in 5 examples. So I will just turn off this feature. I couldn't even find this either in Stockfish.

Hi,
I'm watching the Youtube-Tutorial of the BBC chess engine and on one episode, he talks about history moves and in my C++ code, which is structured differently, it actually takes much longer to calculate with history moves. In fact, beginning at depth 8, it's like an infinite loop.

Here is what ...