On the side of the motor unit you will find 2 controls. One is the down limit and the other is the up limit. I would take the cover off and look at what these controls are doing. The down limit is either mis-adjusted or broken. Turn the down limit in the opposite direction of the arrow printed on the cover to correct this if it is not broken. If you remember where the down force adjustment was I would put it back. It affects the safety.

Since this is for a closet all you'll need to close the doors are ball catch/latches. The strike plate goes on the top frame and the ball attaches to the door. Dummy handles are then attached to the door. If you're a novice DIY'er, I wouldn't recommend trying to hang doors as your neighbor suggested. You'd be much better off buying the double doors with a jamb (you can buy them hollow vs solid) and the price shouldn't be much, if any, more. It will definitely be less work. Measure the door openings carefully and allow room for shimming when you're determining the size doors you'll really need. I also suggest you go to a store that specializes in doors since you'll have more selection and probably better prices than the big box stores. We've purchased doors recently and the door supplier beat HD both in price and delivery time. Here is a link that might be useful: ball catch

I figured it out. Problem with adjusting the limit switches was due to a missing pin on a gear that is on the main motor shaft that turns another gear that moves a plastic screw that hits the up and down limit switches. In other words, the internal up/down limit switches were not getting consistant feedback of the garage door position. Nothing that a twisty tie from a garbage bag couldn't fix. So that problem was fixed. The garage door now moves and it now moves up and down without whacking the header going down and the stop limit bolt (protecting the GDO motor unit) on the way up. I knew I was wasting time when the manual says a single rotation on either screw would result in a 2 inch travel change. and nothing I did was consistant. It either hit the bolt or header or it would just HUM and not do anything. I think the original problem of why the belt's tention spring/bolt came undone was due to excessive vibration due to non-sufficient belt tension. As soon as i got the garage door operational, I noticed it was hecka jerky initially going up or initially going down. Mid-travel was smoother. By tightening the nut (collapsing the tension spring) to the 1.25 inches specified in the owners manual seemed to make the garage door much smoother. When I have the time, I'll adjust the force screws down. I think I have them maxxed out right now. I'll also test the safety/reversing feature. For now, it open and closes smoothly. I'm happy. So, while the owners manual didn't tell me to open the thing up, common sense told me to. Also, this unit has a diagnostic feature. When you press the LEARN button, it will light up the diagnostic light and blink. 5 blinks told me the motor was overheated or the RPM sensor wasn't happy. No mention of what the RPM sensor was. I'm assuming something was stuck. Anyways, adjusting the limit switches got it moving and once I cracked open the motor housing case and saw the limit switches in action and saw how misaligned they were, it was a pretty easy fix. Glad I disconnected the door so I could cycle the belt for testing without crashing the door. that made way too much noise at 10PM tonight. Once again, thanks for your help and I hope something in this helps someone.

Jocobe, I think that you are misunderstanding the problem. The upper sash is not drifting, It stays up. The problem is that when the window is locked, there is still a gap. Balances have absolutely zero to do with this, as the materials have either shrunk, settled, etc to cause this as has been mentioned already. Bottom line: the windows are due for replacement. To fix it for now (until budget permits replacement): either add a thin piece of wood to the sill or head, or add additional weatherstripping to one or both. You can buy stick-on foam bulb seal in rolls from the store that would probably do the trick for a while. Shimming the lock/keeper would be another option. Ultimately, what you are trying to do is fill in the frame to take up the "slop" that is present when you move the sashes up and down when they are locked together.