“w/wo the door attached to the opener”…

[Unregistered-Dodgeman]

Jim, if the door stops when the opener is disconnected, then there must be something mechanical stopping the door. Check the slider bar (upside-down “T” bar) that the door slider travels on. Perhaps if your opener has 2 pieces that are bolted together for the “T” bar, one of the bolts has loosened and the slider is hitting it. Also check for loose bolts on the roller track on each side. One of the rollers could be hitting a loose bolt.
Good Luck!
Dodgeman