Character can't jump when pressing a specific button

Hey everyone!

So I have this very weird bug and been trying to fix it for many hours now so I thought asking here might be a good idea.

I have this weird bug: When I jump normally, I can press every button and still be able to jump without any issues, BUT: When the gravity is changed and the Character rotated AND when pressing S then, I suddenly can no longer jump UNTIL I fall off of something.

Is there something simple I am missing? Like some default input mappings?

Any glue or hint would highly be appreciated!

Edit: I can provide video and code if needed.