@Jörgen I'm also not a (Bluetooth) specialist, but I'm willing to help.
And sorry, I'm currently not able to test it because of seasons end.
But I slightly remember, I had similar issues with my Sena 30K. I solved it by connecting my Navi at first, later my Phone as second (if necessary). The Intercom to second Sena 30K to my Sozia wasn't affected.
My priority is to get navigation instructions. The intercom smalltalk with my Sozia has lower priority and may blocked/interrupted by navigation. The Phone may is connected primarily to be able to receive traffic information for navigation App. Friends/ team mates are connected by Mesh.