Hope the community can help make some suggestions...

We have a small device using a 8mm diameter micro stepper motor out in the field, and some have come back demagnetized. I'm under the impression that demagnetization can happen if a stepper is disassembled (this is not the case for us), or if there is an over current (which we need to test for), or if there the motor is subjected to a large magnetic field.

Unfortunately, we don't have a good sense of scale, and most stepper motor advice comes from people with experience with much larger magnet motors. Are smaller motors more susceptible to demagnetization, and why? Looking for root causes of the failures.

Are there other possible sources of failure?