I would reply better but the forum software is awful and ignores being able to paste when using an Android phone. I short... Deco upstairs was going into port 1 of the Switch upstairs. Switched this...

Just as a quick follow up to this. Seems a cable was incorrectly plugged into the number 1 port on the switch upstairs. Changed it so internet DID flow from downstairs to the switch upstairs into...

Yeah, but when I did this, I didn't have any internet at all. There is an ONT box on the wall where the internet cable comes into the house. This is connected to port 1 on the main Deco. There's a...

@David-TP Hi Yes, it was originally set up this way and detected it was ethernet connexted but because if the frequent drop outs of internet -...

@ARGamingPK1 No - the main Deco needs to be router mode as I don't have an ISP router.

@David-TP Hello Current firmware is 1.8.2 (whatever the latest for the M4 is). The switch next to the first (main) deco is a Netgear GS305. The switch next to the second deco is a TP-Link TL-SG108S....