Swim tracking in activity app on Apple watch 3

I've been using the Apple watch 3 to track my swimming for the last year or so, but for the last couple of weeks it has been a little flawed. It does not show current distance / lengths whilst I am swimming though it is clearly recording them as the total distance and length is shown once I finish, is it possible to reinstate it showing the distance and number of lengths whilst I am swimming? as now it remains at 0 until I close the app