Vivo active 5 not recording distance in pool swim at all

My Vivo Active 5 has stopped recording distance during pool swims. It is recording HR and time but the distance stays 0.

I have also had issues with it recording/displaying data during Boat rowing as well. This is all in the last 5 days. Was working perfectly before that. 

I can do a restart and it works for some of the session then it stops again. Watch is 6 months old. 

thanks