Warped tracks is not the problem. Disconnect the door from the opener in the down position. Lift the door manually. Does the door feel heavy that first 18 inches? IF so the door is going to be heavy for the opener to lift, thus making the opener stop. You can cure this by flipping down the cover on the Genie and depending on the model if you are looking at it from the side with the light bulbs you should see two black knobs on the right side. If this is an excelerator, then everything will be on the bottom of the opener and I believe the force adjustments are still on the right side. One of them is your up force. Increase this slightly and see what happens. If the door seems extremely heavy to you, get a door tech out to check the spring system as you may have a broken one or need them adjusted.

The door wasn't heavy at all. I adjusted the up-force and that seems to have done the trick. It opened five times in a row with no problem. Thanks so much for your help.

Is the need for more force an indication that the motor/gears/springs may be wearing out? It worked very consistently for the first three years we lived here and suddenly began having issues a few weeks ago.

You know barnaby I don't really have an answer for that. I see that from time to time to. Customers tell me it worked great for years, I check the door balance and it is good. Some say there is a break in period for springs. I don't believe that because I don't see this problem everyday and if springs break in and make the door heavier I think I would be going around turning up forces up alot more. Usually it is do to someone adding weight to the door. Like a 2x4 across the top section to mount the opener bracket to. ( WHY PEOPLE DO THIS???????? I HAVE NO IDEA??) Other times I can't find an explanation and tweaking the up force a bit solves it.