hello! I have JBL Charge 4, and it have the same problem!! All that I notice after half year of using is that the speaker’s aux volume is saving separately from volume via bluetooth. How it helps me: I simply set low aux volume on the speaker and adjust volume on Device. The stronger is signal, the less cuts would be. Unfortunately, it doesn’t work ideal, but it can helps with 80% sounds you play. So, JBL, PLEASE FIX THIS STUFF!!