8-3/4 help

Well no need to be overly harsh lol.. the guy that was rebuilding the rear for my friend does know what he's doing.. my bud was helping, and learning.. first rear end set up for him... he thinks he may have accidentally caused the problem.. he was sliding the axles in for alignment check one last time before they tightened everything up for good.. says he saw the spider gears move a little but didnt think it would hurt... so he probably changed the alignment.. he said when they tightened it down they heard something snap.. but at first didnt see it.. everything turned freely and seemed ok.. wasnt until he was getting ready to put the chunk in the car that he saw it... Hey .. **** happens.. accidents are accidents.. at least it was caught before going in the car.. I can only imagine what chaos would've come later... Thanks for the help guys.. much appreciated