I saw the video, basically nothing new to what you mentioned here, you perfectly explained the problem in this topic; however, you were supposed to report back the results of moving the miners to another location, which should be fairly easy to do and it isn't just a random thing I asked you to try, it's the backbone of this troubleshooting process, unplug one of the miners, take it somewhere far away, put it outside of the farm if you would, and see if behaves any differently.

The result of this test will eliminate many doubts and it will narrow down the problem to only a few possibilities.