Volume Adjustment out of sync with device
On iOS devices and some Android devices that fully support the AVRCP (Audio/Video Remote Control) Bluetooth profile, the phone and OV volume levels will stay in sync with each other no matter where adjustments are made.
On other Android devices, the OV and the device will adjust volume levels separately. This provides more possible volume levels; however, maximum volume can’t be attained unless both the phone and the OV are set to maximum. If either the OV or the phone is muted then no sound will be heard.