I will assume since it's 25 years old that it's not on a slide-out. A frig on a slide needs a fan to help circulate condenser cooling air.
On a Norcold we had with a somewhat similar issue (worked sometimes) a piece of insulation was flopping back and forth in the chimney vent obstruction the air flow.
I do know if the electric element isn't sufficient wattage it will cause it not to cool correctly, so if that AC works and the gas doesn't, just guessing, if you have spider or dirt dauber nests in the burner they could be limiting the flame reducing heat output.
I've had them and couldn't see it until I removed the tube.