It might be the "jump + shoot down instantly" mechanic but for some reason it seems to be easier in corners or it is just a placebo, this is what i mean:
On yeah.. this ones a bug
Somehow it is happening if you press the both the buttons together. (I want the jump then shoot to have just a little advantage(like the total height achievable would only increase by the radius of explosion).. but this right here is a bug lol) .
Trying to fix it right now.. (EDIT: FIXED IT BY CHANGING VELOCITY INSTEAD OF ADDING ADDING IMPULSE FORCE FOR JUMPING, YEAAAA :D)
Thanks a lot for pointing it out.