Bad MiniCIMs... failing to consistently start?

[ThaddeusMaximus]

We're running into a case where our MiniCIMs (two of them, exhibiting near identical symptoms) have odd starting issues (weak/no torque), and in fact, are bad enough that we can place the motors in an orientation such that they will not start at all, even when supplied a full 12 volts. I'm darn sure it's not a motor controller issue.

To add to this, they will run perfectly fine in one direction, but see this sporatic starting in the other direction.

Some background on the motors:
The wheels attached have been running as flywheels on a shooter, direct output. A 1/2" hex output shaft was press-fit onto the end of the CIM shaft. The setup is very quiet, but beforehand they were run through a bunch of adapters that resulted in a very messy and rumbly situation.

Has anyone encountered anything like this, or have any recommendations?

We're going to be replacing the motors and doing the press fits for the next hex adapters by taking the CIM and windings out of the motor, so we press on the shaft itself rather than the bushing (if for some reason we were causing damage beforehand).