Okay, so I brought one of the 127 s4's into the house to the main router. It is working in there. So, it obviously has something to do with the wifi extender. I connected the ethernet cord directly to the wifi extender (the ethernet splitter was disconnected) and it still does not appear to work that way. I wonder how 2 can run fine off of it and then when I turn those off and try to run the other it does not work
Does your WiFi extender have some sort of configuration? Look for any "DHCP forwarding" options. Perhaps it doesn't do that by default or it doesn't work properly.
Another option is to connect the miners one by one to your router and set them up with static IPs, then move to the garage - chances are they would work then.