-Pvr and second box hardwired to modem
-google wifi used for rest of home
If the screen is black it sounds like it could be a symptom of a HDCP handshake issue with your TV. Try changing the resolution from 4k or 1080p down to 720P in Menu > Settings > Screen Aspect Ratio. Keep an eye on it for a bit and see if that helps. I've seen it resolve a few issues like this. Trying a different HDMI or better yet switching to component cables could solve the issue as well.