Then I would suspect that the relay on the receiver is sticking but
make sure that none of the internal wires are being pinched under the
motor cover (but since it is a plastic cover i don't think that would
be the problem).

Disconnect the receiver from the opener & see if the phatom operation
goes away (of course the transmitter won't work). If the problem goes
away try cleaning the relay points or if that fails replace the
receiver.

Doordoc