I've seen that once or twice before. No idea why it happens. SUPER rare, but I've seen it a couple times. Maybe the gear was put in backwards? Not sure, but that could effect how much of that splined end is in the box. Its not really going to hurt anything. I have one buddy in Utah that has one on his Ranger that does it, but he has thousands of miles on the same boxes and axles, and never had an issue. Its already clearanced itself at this point, so I'd just clean it out good and put some fresh oil in there and run it.