Volume drops on receiving end using Bluetooth headset

[AC Question]

I used a Zelher P20 headset with a galaxy S5 & S6 and Iphones 4-5&6. Works perfectly. I upgraded to Galaxy S8+ and it intermittently drops the volume on the receiving end of my call. I may 20 minutes or 2 minutes the problem has no logic to it. It does this whether I'm driving or sitting at home. I've got 5 bars of signal, done firmware update, unpaired/repaired device. Tried different headset, still does it. But it's perfect on the iPhone.

Any ideas?