I once had similar issues in our 2 Hopper 4 Joey system. Resolved them by assigning dedicated IP addresses to each Dish Hopper and Joey. Even though cabling was perfect, the Joeys would revert to trying to connect to their Hopper via IP rather than MoCA. So whenever the home Cisco router assigned new/different IP addresses, the Joeys could not find their Hopper. With the fixed IP addresses, the Joeys always "knew" where to find their Hopper.