Originally Posted by
Bob Dopolina
If it was as described, a cheap arsed alloy stem meant for cheap arsed alloy bars then there is a good chance that the stemp clamp was not 100% round and/or the mating surface was not designed for carbon and concentrated all the clamping force in too small an area.
+1. I think using a stem that's not designed or intended to clamp a carbon handlebar is the likely culprit.