Misc Warn manual hubs disengaging

[Dirt ball]

Hey all, my 77 CJ5 . Manual Locking hubs 6 bolt, Warn M195A - I have used 4wd and manual hubs many times before, but new to the CJ. was out on Silver Lake Sand Dunes for a few days, on my last day I peaked one of the bigger dunes and just coming back up a smaller hill. My RF hub disengaged. would not reengage. noisy in 4wd with hub in locked position, but not with the hub unlocked. sounds like splines not seated. back home, I expected to find the internals of the hub to be in pieces. Nope. took every thing apart, cleaned and inspected, No debris, no issues found. reassembled the hub, still will not engage. the dial still spins easy as it should. took it back apart, reassembled it in the engaged position and tried it again. now was staying locked. I figured I would just leave that hub in the locked position at all times. did some more wheeling and it disengaged again. front hub bearings adjusted properly, no cracks, chips, damage of any sort found to the splines or locking mechanism. everything slides easy with no issues working all of the splines individually. What am I missing?