Did you ever get anywhere with this issue you posted? Trying to get your Savi W730 to work best with the DX80 using the EHS APU-72.
I have the same set-up, but with the W740. Sometimes things work well, and I have learned the little work arounds to help with some shortcomings. But then other times weird things happen that I cannot pin point. Like lately while on a call with the headset and DX80 the volume of the audio I am hearing in my headset just gradually fades to quieter, and quieter. If I switch back to the DX80 speaker, audio volume is fine.
On a related note, which dial settings are you using on the base of your Savi (for the DX80)?