Special jumps don't work with some keys

[ObaniGemini]

Special jumps : kick-jump and impulse jump (on-floor)

You can't do those special jumps probably because of the engine not detecting the keys to be pressed both simultanously, and a directional key.

After investigating a bit,
U : up
L : left
D : down
R : right

\\ ULDR

in ZQSD this works if you stop pressing S
in ESDF this works if you stop pressing D
in RDFG this works if you stop pressing D
in TFGH this works if you stop pressing H
in YGHJ this works if you stop pressing G

I don't really understand the relations to this and didn't do much more investigations (I'm on AZERTY btw). Maybe there's some kind of priority on some keys ?
Everything I know is that sometimes it will work if you stop pressing down at the right moment, sometimes if you stop pressing the left key at the right moment.
I really don't get it. With some keys it works all the time (e.g : spacebar).