Why will the remote open my Linear garage door operator, but not close it?
If you get 3 flashes of the courtesy light and you have to hold down on the wall push button to close your door, you are definitely having a problem with your safety beam circuitry.
Check the beams for lights (green on the sender, red and green on the receiver). All lights should be on bright, not flickering. Check the lens on the receiver and the sender (no lens) for dirt or cobwebs.
Check the alignment by pointing the receiver at the sender, then going to the sender, rotate down until the red light on the receiver starts blinking, then up until the red light starts blinking, then split the difference. This should give you the best possible alignment.
It is also possible that you have a wiring problem, such as a high resistance splice or a staple causing a partial short, or the beams themselves are bad.