@Eliaquim This is a very confusing bug to track down...
I tested a lot and I was able to replicate the issue once. It really is quite strange. However, I'm not able to replicate the issue enough to debug it well. I suspect that it might be related to diagonal input (because multiple inputs are added, maybe it is not getting cleared properly).
I added a parameter so that diagonal input must be specifically turned "on" (better to keep it "off" unless you need it). After I added this, I wasn't able to replicate the issue anymore. However, I'm not totally convinced that it is the correct fix...
New version is uploaded if you want to try. Make sure to open it in the Plugin Manager to "refresh" the plugin so you get the new parameter.
@Black Mamba Yes, you can use plugin commands to hide the UI. In fact, I recently added commands to instantly hide the UI, and you would use these commands in a Autorun or Parallel event on the first map of the game.