Bobcat 337 - Travel Motor Drop Bearning

I had a Travel Motor on my Bobcat 337 rebuilt in August 2013 completely with new shafts, seals, piston assembly and a new cover Reason for the rebuild is I had a external (high pressure) release of hydraulic oil spraying oil through the cover that was cracked. After breaking it down the previous owner and done should very "shoddy" work He had the shaft welded ad machined and had attempted to seal the inside of the cover with some type of white sealant to prevent it from leaking. Now the it appears from my Bobcat dealer that it has dropped a bearing causing it to break the cover and is leaking the same as before the rebuild. Can anybody tell me what would cause a bearing to drop. I am hoping that the Bobcat Dealer will cover this under warranty. Any comments or insight on this would help me identify the cause and allow me the opportunity under any responsibility relating to the rebuild. Thanks Bubba