Originally Posted by
mechBgon
...check your derailleur limit screws, particularly the Low screw on the rear derailleur (
Park Tool's how-to). Because reasons.
This was an expensive oversight, I think the final bill is around $300 (including a tune-up to fix a bunch of other assembly/tuning issues).
I'm unclear if this is your bike or a customer's.
If this is your bike I'm sorry to hear of your bad luck.
If it's a customer of yours, I'm surprised that you believe that they did not mess with those little screws that don't seem to do anything. ;-) As you gain experience in customer service, you'll find that people strategically forget anything they've done to contribute to the problem.
Re the bottom bracket: Dry lube is usually used in that type of factory setting. I'd expect those general assembly factories (used for ~90% of bikes sold through LBSs) use the same procedure.
FWIW, of the half dozen BD bikes I've assembled, none have had the limit screws off far enough to drop the chain. Only slight adjustment to them or the RD has been needed for them to work to my standard.
The front usually required more attention, but again, not the limit screws.