I have a (hopefully) minor issue with my garage door opener. There is a small wire that runs from the motor unit along the rail to the center top of the garage door that has come loose. After this happened, the garage door won't stay shut on it's own without hitting the button again at the bottom of the cycle. This wire almost looks like some sort of ground wire. My question is, how does it attach back, and why did it come loose to begin with? It obviously maintains a sensor of some sort (and I obviously don't know much about garage door openers).

Thanks for any help,
Steve