Vivoactive 5 not recording new 1km record?

When I got my new garmin, it recorded a 1km time for me. I have this visible in the connect app. Since then, I have gone on to do many more runs, each with 1km recorded in times that are much faster than the original 1km record.  I get no notification on the watch or the app that I have a new 1km record. Why would this be, when I know I'm running faster and the 1km segments of my 4km runs are showing in the app as quicker?

Thanks