Likely cause: Load had increased. What to do: Ensure that the load has not changed. Measure the amp draw of the motor against the full load amp rating of the motor. If the amp draw is higher than the rated one, the motor is undersized for the application. Likely cause: Motor controller not properly set. What to do: Check controller manual for adjustments. The torque and/or IR compensation settings may need adjustment. Likely cause: Motor may have an open connection. What to do: Inspect the armature for an open connection Likely cause: Brushes may not be seated properly or worn beyond the useful length. What to do: Verify that the brushes are properly seated and measure their length.