Yeah, someone else said the same thing and apparently it has something to do with some old and/or cheap keyboards. It doesn't happen to none of my devices so it was a surprise to me. I've added WASD controls so hopefully it works better. Thanks for playing my game btw :)
Edit: If you are still pressing the 'Up Arrow' while you press 'Left' and 'Spacebar' it won't work on some keyboards. There's no reason to press the 'Up Arrow' and the 'Spacebar' at the same time though.