Yeah I guess that's from my game,
If the bug happen a lot it would be easy to debug, but because it happen only sometime it's hard to debug.
A problem is that I use a game engine in js I've made in 2013 didn't touch the code for ~7years and decide this year to support JavaScript in a generic game engine in C on which I work, so I have like 3 layers of key handling to debug (1 in my game engine in C, another in the one in js, and the part that really do the key handling ).
Also I've learn js while making this engine so a lot of code are ugly...