https://www.metv.com/stories/jim-naborss-comedy-chops-made-him-the-envy-of-his-co-stars

Gomer was so funny that Andy and Don were secretly jealous.

https://www.metv.com/stories/jim-naborss-comedy-chops-made-him-the-envy-of-his-co-stars

Gomer was so funny that Andy and Don were secretly jealous.

The information concerning Don doesn't surprise me, I've speculated that once Jim got the spinoff series, Don's days on TAGS were numbered. Jim had essentially leapfrogged over Don in status. Don's contribution to making TAGS the monster hit the show was towered over what Jim had contributed yet Jim not Don was now the star of his own spinoff series. To stay with TAGS beyond the fifth season Don was going to have to get something more than just a raise. He wanted a percentage of ownership and Andy already had his deal with CBS for three more years with or without Don.

With respect to Andy, I was unaware he had a falling out with Jim. I wonder if things were really patched up between the two, they worked together a couple of times in later years but Jim never appeared on Matlock, and his part in the reunion film was small, it could almost be described as insignificant.