Gate Open and Close Stop Positions Keep Changing

The limit switch lever may be bent and is not contacting the limit cam nut at the correct location. The leading edge of the limit cam nut should depress the limit switch lever well before it reaches the peak of the lever. Gently adjust the limit switch lever so that the limit cam nut depresses it before reaching the peak.
The limit cam nut may be jumping threads on the drive shaft. This can happen if the limit cam nuts were cross-threaded onto the drive shaft, causing thread damage. Replace the limit cam nuts and the drive shaft threaded collar if necessary.