This problem has also been reported with TomTomGo on the TomTom forum.
So it is not a device problem.
I have tested it on 2 other phone with Bluetooth and a smartwatch and it does the same thing.
It is two easy to always say it is the phone or table that is the problem.
TomTom is very good at saying that.
More than likely there is a bug in both apps from TomTom that cause this problem.
But like I said no big deal I just use another phone without Bluetooth running with the app and all works with no problems at all.
PS:
This is also 2 Bluetooth pairings going on here.
First Phone and watch
Then Phone to hands free.
Incoming calls and messages work with no problems.
Can talk to a person with hands free.
Only no voice with TomTomNDS or TomTomGo both have the same problems.
I quote what TOMTOM has said about this problem:
"TomTom International BV30 July 2019
Hi Alan The app streams audio instructions via BlueTooth using the A2DP audio profile. There is also HSP (Handset) and HFP (Handsfree) which the app does not use. It may be that this is using the same channel as the radio. We have fed back your comments to our development team, thank you for your review - TomTom Team"