The answer could be in the Target software.
When you Bluetooth stream with phonak, they make a decision on 2 different configurations:
Media speech + mic
Media music + mic
If one works ok, I’d look at changing the programme options from the one that works badly, to the one that doesn’t.
In my P90s the only noticable difference is that Media speech + mic has “Soundrelax” at 8/20 whereas Media music + mic is at zero. As for the MPO/Gains, music has higher gains in the mids and lows.