Oh I didn't consider that someone might be holding S. I was under the impression that players would only be tapping S when they need to fast fall. Is that just a more comfortable way for you to play the game, or did you think you had to hold it to fast fall? That's a good point though, you definitely should still be able to jump even if you're holding S before you initiate the jump. Next time around I'll be sure to mess around with all kinds of inputs to try and squash these bugs before the jam is done. Thanks for the feedback!
Edit: I tried it out and I wasn't able to replicate your results. Maybe there's a difference in our keyboards?