@Kevin_Z 

and here we are again: speed dropped to 90Mb even after swapping main/slave Deco

as usual when it happens, disconnecting/reconnecting the ethernet cable between Deco and Vodafone Power Station fixes it

actually:

- disconnecting/reconnecting cable from Deco did NOT fix the issue

- disconnecting/reconnecting cable from Power Station did it

@Kevin_Z 

and as usual, two days after "fixing" the issue, speed dropped again to 90Mb

trying now a different ethernet cable. see you in a couple of days 

@Kevin_Z 

took almost three days, this time, but... here we are again to 90Mb

so... so far I can rule out (on the hardware side):

- ISP's Huawei ONT (connecting directly to it doesn't fix the issue)

- ISP's modem/router (they replaced the original one with another to no avail and tried different LAN ports on each)

- three different ethernet cables

- two Deco M9 units (swapped main/slave... no change!)

- Deco's M9 ethernet ports (tried swapping cable between both: still...)

once more: it only happens when Deco is part of the network!

if I connect wirelessly to ISP's modem/router I get full Gb speed (500~800Mb actually)

all I can think of is some software issue Deco M9 has with these (Huawei?) modem/routers:

- Vodafone Station Revolution (the first one I was given by ISP)

- Vodafone Power Station

please HELP! 

oh... forgot to mention: all speed tests are performed by the FingBox I have in my network

among other thing it does, the FingBox performs an Internet Speed test every few hours. and keeps an history of them ;)

@Kevin_Z 

one more week later: no more internet connection sped drops (... so far! fingers crossed)

can't believe it's just because of yet another ethernet cable and the three I tried before this fourth one were all defective but...