This sounds as if it is an opener problem: The door is going just slightly passed the "down stop" position within the controller, actually going just a bit past the micro-switch which stops the controller motor. The weight of the door makes it go past this micro-switch, the the controller recognizes that the switch is not made, puts the controller into the "raise door" mode until the switch is satisfied. All that is needed is some fine-tuning on the door's "stop-down" and "stop-up" adjustments. Remember: If you adjust one setting you will more than likely have to adjust the other just a bit.
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