This issue has been observed on the Android HTC One SV. When a user creates a Pattern, PIN, or Passcode that does not meet the minimum requirements enforced by MDM, the device prompts the user to create a stronger passcode which meets the criteria. 

If the user does not set a stronger passcode when initially prompted, they are prompted again 1 hour later.  If the user still fails to set a stronger passcode, the device will begin to prompt the user repeatedly. However, the device does not give the user enough time to enter a valid passcode before it prompts again. The result is that the user gets stuck in a loop attempting to update the passcode.

To resolve this issue, the Administrator can assign to the user a policy suite without passcode settings in place. Once the user has updated the passcode, the administrator can reassign the original policy suite.