Picade spontaneously triggers wrong buttons

Hello - new Picade user here. I just built a Picade kit and I’ve been enjoying it for an hour or two. However, it has suddenly picked up a bad habit of spontaneously triggering a few buttons when moving the joystick or pressing other buttons. I first noticed that Mario in Super Mario Brothers spontaneously jumps if I’m just walking right and not pressing any buttons.

I’ve checked the wiring and don’t see any loose connections or shorts.

Any ideas?