Here is the layout of my network if this helps
Modem -> Main Deco M5 -> Unmanaged Switch -> Second Deco M5, Main PC, Media Server
So my second Deco M5, main PC, and media server are all on the LAN for efficiency where I need it. My problem is that if I lose connection from my modem, the wi-fi and LAN seem to disconnect completely. Before I switched to the Deco Mesh M5 I had no problem using the media server on the LAN if we lost internet from the modem or if the power went out or cable was down. The modem, switch, and main Deco M5 are on a battery backup except for the second Deco M5.
Of course I contacted support and they gave me the generic answer of "If you lose connection to your modem, you don't have internet access. Also try updating the firmware"; basically treating me like a four-year-old that doesn't know at least a little about what they're doing...Regardless, my local network is pretty much designed specifically around the media server access whenever I want so I don't see a point in using the Deco Mesh system. I won't disregard TP-Link all-together but I won't hesitate to return, sell, or throw away these Deco M5's if this is just how they work.
Any help or advise would be appreciated, thanks!