Large white circle on Qgroundcontrol map screen

Flying a mission today the Qgroundcontrol screen depicted a large white circle I’d never seen before.

I thought it might be a fence - but I don’t have any defined.

Any suggestions on what it might be?

ADDENDUM: This mission was my first time out with my new HereFlow optical flow sensor and Lightware LW20/C lidar sensor. Not sure if that has anything to do with the white circle - but it’s the only things I can think of that have changed.