This is gonna sound crazy, but make sure you have no Android OS cellphones running on the WiFi.
He's not wrong about the android phones or tablets on wifi affecting the Blocks. Some routers handle it better than others.
I've read that! Also seems silly. But possible I suppose. Depends on the router, as said. I can see how some poor router firmware might cause issues. I don't experience that issue personally. I am running Cubes at the moment and have anywhere from 6 to 11 Android devices connected to the LAN without an issue.
Cubes run on High @ ~ 37 to 38 GH/s.