Originally Posted by HillRider

Well, waddaya know. This is the first Shimano hub I've ever seen with bearing cages. So, it does seem to be an assembly error on Shimano's part.

I'd replace all of the bearing balls with those from the same lot number rather than just adding one to make up for the missing ball. I'm also one of those who recommend a full compliment of loose balls and discard the retainer.