Music Plays During Voice Search (Bluetooth issue)

[Spot1000]

I have a Toyota with a bluetooth car stereo (using an a2dp connection) the car also has a mobile/cellphone connection (using an HFP connection). When I play music, it comes through the car stereo perfectly. When I press Spotify voice search button, the car stereo stops, the seach beep comes through the mobile connection AND music begins to play over the search through the mobile/cellphone connection. For me to use the voice search, I need to speak over the music. Anyone else have this issue?

Here are detailed instructions:

When connected to Bluetooth
Open Spotify on iOS and select a song
Car stereo plays (a2dp starts)
Press voice search in Spotify
Car stereo mutes (a2dp stops playing)
Search confirmation beep plays (hfp starts)
The song that is paused starts playing through hands free speakers
Spoken words appear on phone
Search works as expected (hfp stops)
Car stereo plays new song (a2dp starts)

Things I've tried already:

Reboot the phone

Restart the car

Upgrade the phone OS

Delete the Spotify app, download again, install

Confirmed Handoff is off

Plan - Premium

Country - US

Device - iPhone 8+

Operating System - iOS 11.4

Spotify Version - 8.4.53.689