Sorry for the late feedback.
> The double jump issue never happened to me during tests and you're the only one that mentioned it.. how could I replicate the issue to check it out?
Just double click fast or hit space bar twice. The leverage of doing this (as far as could visualizing notice) is to go one tile higher than that high jump (holding space all along the jump to go higher).
Also, is this meantime read and saw a couple of videos about "input forgiviness" mechanics. I think this is a gret addition to any platform game. You could implement some of them when you reach a more advanced developing stage of your game :)