Forerunner 955 Open water Pace - display Issue

I have rearranged my screen to show pace and distance. Yet when i was swimming, the pace showed 0:54.  When it should have showed between 1:40 and 1:54 depending on the stage of my swim.

Why is not showing my actual pace at that time?  Average pace on another screen works fine?

Is this because the pace is not set /100m on my watch or is there a bug?

I cant find any way to change this on the watch or on the mobile app.

Any thoughts please?

Thanks.

John