Gus, if it works at all, it must be a problem with settings. The general rule with DC/DCC engines is that if they run okay on DC, they should be just as well or better on DCC, but with more do-dads. If they don't run well in DC, they'll probably be entirely crappy in DCC.
So, if you have a decoder in a B'mann engine, and you are vexed, it suggests to me that the various CV's that control movement need some spanking. Figuring out which, and how many swacks, is the puzzle. It generally means getting into the manual for the decoder and pondering your next best guess. Try dither, torque compensation, V-Start, and so on.
-Crandell