Was any updates done to the phone before it stopped working correctly? I had the issue with carplay in my 19 MDX not working and causing the info-tainment system to disconnect and restart every 5-30 seconds from IOS 12 to IOS 13. It wasn't until months later with update IOS 13.2.3 the system started working correctly.
In the meantime, I still had my iphone 6S plus connected by bluetooth, had Waze on the phone, and got Waze commands/warnings on the front MDX speakers.
I would also try apple maps, google maps, and Waze to see if one of those apps had an update that effected the bluetooth navi audio because of an update.
Dad - 19 MDX Sport Hybrid Adv Fathom Blue Pearl w/ Graystone
Mom - 18 RLX Sport Hybrid Brilliant Red Metallic w/ Ebony
06 TSX w/ Navi (Totaled Oct/19), 08 RDX Tech (Daughter), 11 MDX Adv/Ent