@Hisham_A You can use powerline to avoid WifiBackhaul down speed. Or ethernet from main deco. 8 ports switch linked to main deco and all others deco's. i have 300mpbs fiber here and got 300mbps in...

@rmnayve Here you got 1.4.2 version: https://community.tp-link.com/en/home/forum/topic/187114 And update via web gui.

@Janingo No, you can't read at Deco App, but have some app to do this. Windows/Mac: https://www.netspotapp.com/ Mac: https://www.adriangranados.com/ (Wifi Explorer) Wifi Explorer o Mac, but rememer...

@Hisham_A yes, any unit connect at any unit in range but for best performace with wifi backhaul use any software for meansure SNR signal between units, if you get plus 24db of SNR wifi backhaul works...

@mldemeo No, you don't need change anything ... just move your units....

@VCL your deco network have ipv6 enable? If yes, try disable ipv6 and check if solve your problem. I have a lot of problems with ipv6 when enable.