huh?
is your chain really drooping - hanging?
shifting on a bicycle requires a certain order or progression, either ascending or descending on the chain-rings, accompanied by steadily pedaling through the shift. sometimes random shifting that does not follow that progression, or not pedaling while shifting, will result in a thrown chain.
given the caliber of components on this bike i would suggest that the problem may be due to operator error?
bottom line - i think you must have thrown the chain?
*sdr*