Motor Brake makes G320 act wierd

The motors I am using now with Gecko G320's have build in brakes
(they came off of a robot)
Depending on when I energize the brake it seems to cause the drive to
falut out and not be able to recover. The funny thing is that if I
just lightly twist the motor shaft (they are on the bench) the drive
resets and everything is fine.
It's not a problem at present I just make sure I have the brake off
when the drive starts up.
Anyone else seen this?
Joe V.