Wrong distance reading

Hello, I've noted that distances in my Garmin Instinct are completely wrong. In my most recent run, the Instinct recorded a distance of 6.06km. If I plot the same route I run on Explore, the distance turns out to be 9.6km: and note that my rough track plotted on Explore is underestimating the true length which is probably a bit above 10km.

Of course I wait for a GPS fix before beginning my training. Software is updated. Can you help me troubleshoot this? Thanks