Apple AirPort Extreme ver 7.6.4
Apple Time Capsule ver 7.6.4 (first unit)
Apple Time Capsule ver 7.6.4 (second unit)
Apple TV Model A1427/Apple TV Software 7.0.3 (6917)
I have been using these devices (and other wi-fi connected devices on my network) for over a year. Generally all works smoothly with the exception of the above noted Apple TV unit which periodically suffers from disconnections and usually exhibits slower downloads than other Apple TV units in our home.
The configuration is shown in the attached image.
What doesn't show in the attached image is the Apple TV (aTV) unit which since yesterday has stopped connecting to the router (Airport Extreme).
I can connect wirelessly from my MacBook Pro (MBP) to the two Time Capsules, which are set in Extended Network mode, but since yesterday, their front-panel LEDs are blinking amber and I'm getting the error message "The Airport Base Station was unable to extend the wireless network".
The Airport Extreme is on the main floor of the house while the two Time Capsules (TCs) and the Apple TV unit I'm referring to here (not one of the two listed in the attached image) are located in the basement. The TCs and aTV are well within range of my router. The signal strength on the TCs is 'excellent'. Since yesterday, the connection was dropped on the aTV so it is now showing zero signal strength. Usually it shows 'excellent/full signal strength'.
I suspect among other things that I'm not configured properly overall because my wireless transfer speeds (when I backup or xfr between computers and TCs) are quite slow for what is supposed to be blazingly fast hardware on an 802.11n network. It took close 24 hours to back up a 750GB iMac across this network last week and my MBP is similarly slow to perform it's backups. I'm guessing this may have to do with communication conflicts or delays between the router, TCs and connected delays (in other words, if I was connected to just one of the devices, say just to the TCs, and not to the router, things might be quicker, don't know; reason I didn't set it up that way is that I will sometimes power off the TCs for an extended period of time).
I've tried powering off the TCs and aTV and then power cycling the router, then powering back up the TCs and aTV (which normally resolves issues) but this hasn't fixed my problem.
Any idea how I can reconfigure this to work properly (i.e., re-establish dropped connection, improve network speed, improve stability)?