Transmission main shaft issue

[Durango]

Last year I bought two main shafts and one sliding gear from Snyders. One shaft and gear were installed in the original Transmission. On the first road test it kicked out of 3rd gear when coasting to a stop. I drove this way during the touring season until the transmission locked up in 1st gear. When the transmission was opened up I found the roller bearing was destroyed as well as the input shaft and new main shaft. When comparing the original main shaft with the new damaged one I found that the spacer ring was not as close to the splined portion of the main shaft as the original leaving zero clearance ( end play ) for the end cages of the roller bearing. This was due to a longer radius than original between the snout and splines on this new reproduction main shaft.

This is a trap because when assembled on the bench all goes together as normal and turns freely by hand when checking the function.

Les Andrews manual says that if the spacer ring is left out the roller bearing will be destroyed, that is because the inner cage of the roller bearing will ride up on the radius and be destroyed as stated and has nothing to do with the above