My 5 slot Lesser Hiryu went wild (too many failed commands when apparently not happy). Not sure why it got unhappy, never has happened to me before (120 tame, vet, lore). I quickly retamed, fed, and stabled. A few days later I check the stats and its Wrestling, Tactics, Resist, and Anatomy were all set to 77!! (they were at their respective caps). When I finally was able to get a GM to check it out I was told he could find nothing wrong with the pet, he is not able to adjust skills and "Sorry this happened." He will be reporting it to the Devs.
Very sorry to hear this, Hagrid.
Thought I read something about people exploiting pets by releasing them so they "changed things":
All pets which have been exploited by releasing or death will have the following stats reset and incur a penalty to their advanced pet training. Strength, intelligence, dexterity, hit points, stamina, mana, base damage, and all resists will be reset to defaults.