Oh wait, NO RESOURCE message error. And you are using 4K HDMI output, which probably means that when watching 2x2 they are using the main streams, not the sub streams.
What resolution and bitrates are your cameras? You are above the max decoding specs your NVR can do. Not sure if there is any setting to force the substreams when yoiu are doing 2x2 on 4K output.
(when you are using iVMS @ 7:09 you are watching the sub streams)
I had the same issue when running on a 1080p TV.