Played on keyboard (don't own a controller), and jumping on the ground was extremely inconsistent. About 60% of the time, Wriggle just wouldn't jump at all. This wasn't an issue for walljumps or jumping from water, just off the ground. Same thing happened when I uninstalled, and it's an issue on both 64 and 32-bit Windows. I was able to complete the game by finding workarounds and kicking a lot, but it was really rough. It's a shame, because everything else about this felt really polished.
Viewing post in There She Goes, Wriggle Nightbug! comments
Had the same issue: it's due to the game's uncapped frame rate. I had my monitor's refresh rate on 144 Hz which is the default, and seeing the inconsistent jump inputs I went "What if?" and set my refresh rate to 60 Hz - now the jumps are fine.
(I'm used to seeing games with uncapped frame rates so I know one when I play it)