The extra bearing is for worst case scenario. We have never had one fall out yet, but understand the nature of manufacturing in there is always 1 in a million that will come out somehow, dropage, extreme use etc.
Hey @Orang3j3llo - Sorry to hear that! All the tops shipped with the extra bearing just for this scenario as they can fall out with use, drops, and temperature changes. Use a spot of super glue and then press/insert the bearing back into the socket. If that doesn't work we'll be happy to exchange for you. Cheers -