Oh... Thats actually part of Pico8! I used BTNP(x) which means, that it should (!) only react to Rasing etch (so actually pressing down once). What it actually does is only react once and then gets true again after some time is passed. I don't know why that is. But I might actually want to fix this somehow maybe check with an own function if X was released at least once since last jump.
Sorry :D It seems I don't have that habbit.
Thank you so much for gaming and giving feedback! this is so important for me.