Axle popped out somewhere toward the end of a 100 mile ride and didn't catch it before destroying axle end. Machine did make it all the way back to camp, we'll call that a win.
After inspecting the circle clip, there were two small shavings sticking in the grease inside the transaxle, at the open bore past the spline. examining the circle clip, it appears they were shaved from it on installation as the usually round shaped clip has a flat spot on outside perimeter (looking at under magnification). Circle clip was formed into the groove and did not have any "spring" to it. Hardness files I have show the clip is almost soft, compared to the stock ones that were on the original Trail axles. SATV sent me a replacement axle, circle clip on it is comparable to hardness of stock, so we should be good to go.
If anyone is using Rhino 2.0 axles from SATV on the rear for these machines, beware they do not come with the 1-1/4 ID x 1/16" o-ring that seals dirt out of the transaxle spline.