1- Unpair everything. Pair just your Sena and the Nav and see what happens. Your phone setting may be the problem.
2- On the Google, search ADVRIDER: Nav V MP3 Music. I recall having a similar problem getting my music to play thru the Nav V and AdvRider had the solution.
Although I got the Nav V to play my music I no longer use it. It became a pain to constantly convert my newer music to MP3. I found using my iPhone for music was a lot easier to live with.