Losing audio while galaxy S4 is in dock mode

Just hope that you can help here.
I have a Samsung Galaxy S4 mounted in a dock (Ibolt Xprodock) in the car. This is connected via the mini usb port to the cars aux socket to play through the car speakers. I also have a Parrot MK3100 Hands free bluetooth for phone calls.
The problem I am having is when I make a call through the Hands free, when the call has finished, the music audio of whatever was playing through the phone outputted through the mini usb socket never resumes correctly. Always seems to resume using the phone speaker.
The phone has to be rebooted to re-enter the car dock mode.
Is there a certain setting within the app that I should be using?

I am using the Soundabout Pro latest version purchased last night.

Thanks
Julian

The question is what does SoundAbout "think" the audio output is.

Can you try the latest Beta version here:
https://soundabout.forumotion.com/f8-download-beta-versions

After the phone call is finished, take a look in the status bar notifications (up top) and drag it down. What does the SoundAbout notification say the audio output is set to?

Does is say "Speaker in use for media" or "Dock in use for media" or "Wired headphones in use for media"...etc?

I shall give it a try.