Diagnosis
Control board memory corruption or power fluctuation. The unit loses its programmed limits, defaulting to a short travel cycle.
How to Fix It
Perform a full system reset. Unplug the opener. Disconnect the red learn button wire from the back of the wall control panel for 30 seconds. Reconnect the wire and plug the opener back in. Reprogram the up/down limits using the limit adjustment screws. Test the cycle three times.
If That Didn't Work
A failing logic board backup battery or capacitor is not holding the memory. This is internal to the main control board. The board requires replacement.
Heads Up
After resetting limits, always test the safety reversal feature. Place a 2x4 board on the floor under the center of the door. The door must reverse on contact.