Hi Billy
Not sure if I'm on the right track with your Loco
but as it is new it may need a little more running in before conversion to DCC , things are probably a little tight in the drive
and the BEMF is trying to compensate
I get the same problem with older loco's that need a new backplate ( so one new bearing that can be tight)
and need to run them for while before pluging the decoder in
hope this helps
Regards Zmil