Problem 1. Have you checked the batteries? I know it's basic but I have to ask. Problem 2. Sometimes the installers use staples that are not insulated on the wiring for the wall control. Make sure these have not cut through the insulation. This can cause intermittent operation. If you live near an air force base there can be other problems but I really haven't an answer for this. I have only heard the frequency used by opener companies belongs to the military and they are taking it back. Problem 3. Make sure the door sensors are pointed directly at one another. There is a small light on each sensor and they both need to be on to work properly. Make sure they are not blinking ever so slightly. I don't think your problems are related but...........

If the opener was manufactured prior to 1993 it did not come with sensors. It sounds like you may have a combination of problems. I would first check the door springs to make sure one of them isn't broken. Next remove the cover off the motor unit and check the condition of the drive gear. It is white nylon and is just in front of the motor. It should be obvious if it is going bad. On the rear of the motor unit you will find a couple controls. The up and down force adjustments. Increase both of these about 1/4 turn and see if there is any improvement. The normal life of these units is 10 years so you may have a losing cause here. (There are always exceptions though).

This is usually caused by a shorted wall control or the wiring running to it. You can eliminate them both by disconnecting the wires from the wall control to the motor unit. To eliminate just the wall control remove it from the wall and remove the wires from the back. In both cases remember which wire went where. The short in the wiring is caused by the staples cutting through the insulation. The wall control just goes bad.

The solution posted by GDS above was right on. When you come home and find your door open and you know it was closed before you left earlier, then depending on whether the light (clicker) is flashing or not, you have a good idea where to start looking for a solution. No clicking means that the door was ordered to open while you were away either by a stray radio signal with concidental code, a faulty manual push-button switch wired directly to the opener, or stray electro-static/magnetic interference causing an overly sensitive circuit board to behave eratically. A clicking light means that the motor came on by itself without any 'real' external command and attempted to push the closed door even harder against the garage floor and this triggered the overload protection which caused the door to open and the warning light to flash. GDS explains perfectly why the motor would spontaneously come on by itself without any remote command. The reason as reported above is that there is a double-throw,single-pole metal leaf switch (3 thin metal strips riveted together) which gets activated only when the door moves to its fully open or fully closed position. One switch, two roles to play, thanks to two plastic wands that move up and down with the motor to trigger a stop at either the upper or lower pre-programmed positions. This leaf switch is soldered to the circuit board by 3 joints, and over 16 years in my case, the constant pressure on this leaf switch (several inch-ounces of torque) can cause the solder joints to crack. And so they did in my case, as you need a magnifying glass to see these hairline cracks, but they were apparent to me, having worked in electronics for over 40 years. When wind vibrates the garage door, the vibrations feed back into the circuit board and the bad solder joint(s) temporarily opens the circuit which makes the motor think that it still needs to continue closing the door. Since the door can't be physically moved any more in the down direction, the safety micro-switch gets triggered by the overloaded motor and the door gets re-opened. To repair the bad solder joint(s), you need a 50 watt electronic technician's pencil shaped soldering iron and some thin solder that is designed for electronic work and not for copper plumbing. Overheating the solder tabs on the board will cause delamination. Better to let an expert do the work. Cheaper than replacing the whole board and in my case, I only needed an hour to solve this problem, which would have been impossible without this thread. Thanks GDS. All problems in life should have a posted solution like this one.