Hi, i'm trying to do a basic vlan using a guest network (2.4ghz) to connect all my 2.4ghz band devices to or let visitors use, leaving my main wifi at 5ghz only for phones etc

i've a main DECO M5 in router mode handling the internet connection 

3x DECO S4, two connected via ethernet backhaul and one connected to the M5 via wifi.

i'm using a zyxel gs1200 managed 8 port gigabit switch  

Port8 - Main Deco M5

Port 7 & 4 Satilite Deco s4's

other ports - tv/games consoles etc

one wifi only s4 satellite

i've setup a 2.4ghz guest network with a vlan id of 591

on my switch i've created a vlan of 591 and added ports 7&4 as members of that 802.1q vlan with port 8 (m5) as a untagged member

I've left the pvid as 1 for all ports, if i change this to 591 i seem to lose ethernet backhaul for the 7&4, i'ev tried them separately and each time whichever has 591 drops it's connection.

in either iteration the two ethernet backhauled satellites have no internet connection via the 2.4gzhz guest network, but the m5 and wifi only satellite s4 work, and all devices move to those when they find no internet on the others

am i missing something with the decos?