potential issue with hystogram of depth

I've been noticing weird and erratic behaviors of depth histogram
Starts fine showing local time on X and a green bar with measured depth then goes likein the attached screenshot.  local time would be 15:45 and depth 2.57m but the histogram loos empty amnd on X I got only a bunch of 1:00
 

As I replied on facebook, please check that Depth histogram duration is not 0