I am using 2.1.20 build 2 with 4 V2 cameras and one Pan, all with the latest available firmware.
What I have noticed is that often the Thumbnail
Picture will not update. I go into a camera and view its live feed but often when I come back out to the main screen the thumbnail image is the same one as when I went in.
Once in awhile it will update but to an all black screen. Viewing the camera again will often fix the issue.
Sometimes the thumbnail updates as expected so this is intermittent behavior.