HERE2 GPS accuracy error

Hi all,
I am writing this post to learn about the GPS accuracy error which I have been facing with my Cube Orange setup in the past few days. I have an Orange cube with PX4 1.12.3 running in it. With a ground based setup that I prepared along with the Cube and Here 2 GPS, I have been checking the GPS accuracy and the Geo-fence breaching of my setup. When arming the setup and moving it along, there is a Geo fence breach that happens around 3m for a 10m fence radius, 8m for a 15m fence radius and 13m for 20m fence radius. This constant 7m difference in the accuracy is being consistent even after I tried interchanging the GPS modules and the Orange cubes without changing the carrier board. Can anyone suggest me where and how to find the root cause.