Keep breaking 3rd gear

Since the cluster-gear is only supported on the outer ends...............I'm having trouble accepting the bending countershaft theory. Nor can I imagine that big meaty clustergear itself deflecting. If it was cluster-pin related I would expect 2nd to pop first; that gear is further up the cluster from the back and closer to the center, and since it has fewer teeth, they would be more heavily loaded.
What I can imagine is the mainshaft nose moving up and away, carrying that front bearing with it. There's just not enough support there in those few needle rollers.But what do I know!
I would be looking for a better front bearing, perhaps with more-balls or bigger balls,or something.

Now, I'm no engineer,and this is purely speculation on my part.