companion not gaining xp

[CapnCrunk]

yes i did max his XP in the stables, and yes i did get him to rank up outside the stables. i gave him the onion while still in the stables before the rank up outside the stables. Now he doesn't gain any xp inside or outside the stables.
when i try to train him, a window pops up saying "Further training will not result in additional EXP unless the cap is raised. continue training?" He is rank 13 3stars with 0/2217000 exp.