Problems driving new vendor brushless DC motor

Hi,
I have an existing custom designed brushless DC motor controller and
software that works fine. Today we integrated with a new BLDC motor
from a different vendor. With this setup the motor behaves weirdly,
it seems to work fine in one direction but drives with a strange sound
and reduced torque in the other direction. I've looked at the hall
sensor signals and they look fine and the motor is the only thing
that's changed. We are trying different motor phase wiring
combinations in case that has changed, but no luck so far.
Can anyone suggest what could be going wrong with this new motor?
Thank you,
Fred