Shaft Rear Propeller- Rancher 420

New to this site…looking for help on what appears to be a minor problem. ATV is only 4 months old and I recently heard a "clanging" noise while riding. The problem is with the "Shaft-Rear Propeller" where the circular "cap" has come disconnected from the base of what it attaches to (see photos). This is down by the rear suspension. In viewing the parts diagram of the "Rear Final Gear diagram" I think this is part of the "Shaft- rear Propeller". Dealer says I should be able to easily tap this back into place. Seemed easy enough, and I was able to attach it back on but I can’t get it to stay in place. Its not bent and looks like it should just fit back on, but after I ride again after very short periods of time, it keeps falling off and dangles on the shaft again. Any advice? Pictures attached. Thank you!

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