So I use live Captions and they work fine on video playback and voice notes etc. However on phone calls the dialogue box comes up but there is no captions being presented - even after a minute or two of the call answered etc there is no text. 

This applies to all phone calls not just to a specific number. 

Occasionally turning phone off and on again makes it work but then only works for one phone call. 

As you can see 15 and 30 seconds into below calls do not have any text and these numbers use recorded voice menus so speech is clear enough, the same applies when calling friends etc there is no caption displayed.

I have tried resetting phone, countless restarts and resetting live caption settings 

Thanks