Top half of window won't stay up.

If the window isn't staying up, it is probably a balance issue. The only way to know for sure is to examine both the balance and shoes for any obvious damage or wear. Odds are you have a problem with both, but you won't know until you check.

Either way, once you've singled out the source of the problem, I'll need you to remove the part(s) in question and show me photos of each one in an undamaged state and without any obstruction. From there I can see if anything in our catalog matches.