Elevated gyro bias and scale factor

We are using the MPU-6000 in part of larger system delivered from a vendor. Our testing is showing the gyros have elevated bias and scale factors. With our preliminary boards we were seeing gyro biases around 10 deg/sec. However, the biases for the system are now range from 50 to 300 deg/sec. The scale factor errors have increased from typically less than 3% to over 80%. Some of the axes (mainly the x-axis) are failing the self-test check.

We have ruled out software issues since the preliminary boards still function properly in terms of bias, scale factor, and self-test. The accel performance appears unchanged (i.e. still good) in the larger system.

The vendor states that they followed the proper temperature profiles when building the boards and that no ultrasonic cleaning was performed. It appears to me that somehow the gyros are getting damaged. Any ideas about what has gone wrong? What other questions should we ask the vendor?

Thanks!