You say you adjusted the down limit. You need to try adjusting the down force which is on the rear of the unit near where all those white wires go. Increase this just a bit and try. Now would be a good time to lubricate the track and door rollers and hinges.Don't grease the track. Let me know if this works.

I adjusted the down force and lubricated all moving parts as you suggested. The problem still persists. I disconnected the door from the chain drive and just ran the motor. Even with the door not connected the chain only travels about 12" and then reverses. It's as if the motor is "confused" on how far the chain needs to travel.

It is a sensor problem if the main light is flashing 10 times when the door reverses. If this isn't happening there is a small circuit board with an infra-red detector that causes the door to reverse if it hits an object. If this board goes bad or something blocks the infra-red it will cause this problem. This board is located near the front shaft of the motor and there is a black plastic interruptor cup on the end of that shaft. Make sure the cup is pressed all the way on the shaft and try. The board should not be very expensive and is available at any good door repair company.