@James723 So far the problem seems to have resolved itself. The major thing I did (and I'm not completely sure if it helped) was to reduce all metal / Bluetooth-emitting devices between the main Deco...

@TP-Link 1. Would the satellite Decos become red when they failed to connect the main Deco? Yes, the satellite Deco turns red every 5 minutes or so which didn't use to be a problem. I've swapped...

I just updated the firmware for my Deco M5 V3 to the latest firmware and ever since it's had a lot of difficulty connecting to the main Deco unit. With the previous firmware this has been working...