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My Liftmaster garage door opener was stopping the door several times prior to reaching the full up or down position. The unit end light would blink during each occurance. I had a repairmen come out and he lubed and adjusted the garage door springs. However, the door stopped on the next try after the adjustment. He pulled the garage door unit apart and stated that these are extremely difficult to troubleshoot. That my options were replacing the motor and/or the circuit board, but by the time I replace both it would be cheaper to replace the entire unit with a new unit. He needed to leave for another appointment and told me to think about it.
After he departed I looked at the unit myself and found that the rear light bulb (I use only one 60W bulb even though the unit is capable of one front and one rear) had bubbled up the plastic and actually had several large cracks through the rear of the unit. This Liftmaster had its circuit board in the rear directly beneath the damage, after replacing the circuit board it solved the problem. I would recommend (if the option exists), to only place the light bulb in the front or opposite of where your circuit board is mounted.
After he departed I looked at the unit myself and found that the rear light bulb (I use only one 60W bulb even though the unit is capable of one front and one rear) had bubbled up the plastic and actually had several large cracks through the rear of the unit. This Liftmaster had its circuit board in the rear directly beneath the damage, after replacing the circuit board it solved the problem. I would recommend (if the option exists), to only place the light bulb in the front or opposite of where your circuit board is mounted.