I have a 3 unit BE11000 setup in my 1500sq ft ranch house, and I'm experiencing frequent disconnections on the satellite farthest from the main unit. The house has a fair amount of metal studs in it (as well as aluminum siding), which makes it a bit tricky, but I didn't have this issue with a previous XE system or the Orbi prior to that. 

The satellite LED goes blinking red, and pretty much all devices on the network slow to a crawl; the ones nearest that satellite stop working on the network altogether. It seems as if the satellite continues broadcasting on the SSID, which interferes with the connections to the other satellites that are still online. The fix is to unplug and replug that satellite, but this is inconvenient if someone is sleeping in the bedroom that it's in. 

My current settings on the Deco system are with the same SSID for 2.4, 5, and 6GHz, with the MLO network off (we don't have any Wifi 7 devices). Wireless Network Mode is set to Optimal Performance. I do not have an ethernet backhaul between the devices (and it would be difficult to install this, since it would have to go through the attic). Fast Roaming and Beamforming are enabled. 

Anyone have any advice on resolving the disconnection issue? 

I think the "disconnected, never tries to reconnect, interferes with other stuff on network" is something TP-Link would need to deal with in a firmware update. If a satellite loses connection to hte main Deco, it should stop broadcasting so devices can transfer to the other Decos.