I'm running an Eos which (sometimes) speaks to my Samsung S9 running
XC soar.
I use XC soar as a back up to the Zeus and it's handy for getting a
heading up display which the Zeus currently doesn't do. (windy here)
I get mount problems with Bluetooth if I let the phone pair with the Bose
Speaker in the glider before it mounts the Eos output.
Switching the speaker off, re-booting the phone.
Mount the Eos stack then the Bose stack seems to work ok.
Bluetooth is a bit iffy on multiple device connections.

YMMV, or you may be confusing the stack less by not having in flight
entertainment throwing a spanner in the works.