CMMovementDisorderManager produces CMErrorUnknown

Hello,

I am working on a clinical-grade application with access to the CMMovementDisorderManager API to track Parkinson's symptoms.

Sometimes, these two method calls produce an NSError in the CMErrorDomain with code 103, which appears to be CMErrorUnknown:

[CMMovementDisorderManager queryDyskineticSymptomFromDate:toDate:withHandler:]

[CMMovementDisorderManager queryTremorFromDate:toDate:withHandler:]

This is difficult for us to track down, because the error code is nondescript, and the user info is empty. We really don't have any clues as to what could be causing this behavior.

I'm hoping a CoreMotion framework engineer with visibility into the code may be able to take a look and let us know what conditions can cause this result.

Thanks!

Dan