Thanks for the praise! I did encounter that bug too, I'm pretty sure it was because the weapon box was in the same layer as the ground. It should let you jump again if you shoot down a few times because it pushes you into the air slightly and kinda resets the isGrounded boolean.
In hindsight I agree that it doesn't fit the theme very well. We planned on having some in-game lore which would make it fit a bit more but we ran out of time.