I have a set of 2 Deco M5, and yesterday I upgraded the firmware from a version I don't know to the latest (1.2.8 Build 20190403 Rel. 40244).
I've done the upgrade wirelessly through the Deco app from work.
When my wife and I got home, we started having trouble accessing the network.
We enter the correct password and it take plenty of retries to connect to the network, and it happens in both of our phones, smart TVs and etc..
Additionally, it now disconnect often and making then again it's hard to connect again.
I thought about changing the firmware version, so I downloaded the last version after this one which was 1.2.4 Build 20181106 rel. 48798 for UK.
I couldn't find anywhere on the web a guide on how to downgrade the firmware version manually...