Using modified Comm samples from the CIQ SDK and the CIQ Android Mobile SDK, any attempt at communication from the phone to the Garmin device results in FAILURE_DURING_TRANSFER, while messages go through normally in the other direction.
Also see https://ciq.forums.garmin.com/developer/connect-iq/f/legacy-bug-reports/5144/failure_during_transfer-issue-again-now-using-comm-sample for additional details.