The lag is definitely the biggest issue
The lag issue takes the enjoyment and playability of a simplistic game like this and throws it out the window. I did not however run into the upgrading bug at all, I was able to fully upgrade everything and still able to jump, but when the rope would get longer, and I hit a wall, I would just lag slide down the wall. Thus not be able to play the game for a good minute while the guy just stayed there in a perpetual lag.
I doubt this will get fixed at all, considering the nature under which it was made, but your next attempt should focus on what will be simple AND be able to be played. I don't give a rats ass what my guy's head looks like on little ten minute time wasters like this, but I sure as heck would actually like to be able to PLAY the game.