It flashes because it s hearing the radio signal from your transmitter remote.
Garage door opener signal weak.
If the range improves then the interference is coming from a device in the garage.
Modern garage door openers are essentially small radios that operate at about 315mh and a few feet of extra distance can affect the signal.
Multiple garage door opener troubleshooting test start by unplugging the opener that has good range powering down this unit.
Make sure that the antenna on the motor unit is hanging downward and is not damaged in any way.
Clip the remote control onto a sun visor in the vehicle instead of a metal ash tray or metal dash board that can.
The remotes work by electronically sending a signal to the motor inside your garage allowing you to open and close the door.
Troubleshooting a lost signal on your remote is as easy as resetting the old signal on the motor opener and equipping your transmitters with new signals.
To isolate potential sources of interference turn the circuit breaker off to the garage and plug the garage door opener into an extension cord from another room.
If the bad opener suddenly has good range again then the other unit in your garage is causing rf interference.
Before installing the extension kit move any metallic objects that may obstruct the signal between the remote control.
Any electrical device can be the source of the problem.
Oftentimes when your garage door opener remote stops working it is because the remote transmitter has lost its signal with the motor.