Navigation Audio Promps

Has anyone any ideas why my garmin edge 1030 plus is very temperamental in the navigation prompts. 

Until very recently it was faultless.  Worked fantastic and helped me navigate especially in city's as my eyesight is not the best anymore.  Indeed it assisted me fantastically going through London and Paris on my recent London to Paris bike ride.

It works well for about 5 commands of each ride  then sometimes works for the whole ride other times it stops working.  My phone is still connected as I get  message notifications / calls etc. Transferring routes works fine so it's not a phone connection problem. 

I've updated everything,   uninstall and reinstalled everything and done a hard reset but the problem still exists.  

I messaged garmin who obviously as its out of guarantee offered me a reconditioned one for best part of £200.

Everything else works fine and my  di2,viara,remote connect and work faltlessly 

Does anyone have any ideas of what's going on and how to fix it. Im baffled.