Bad signal choice
So I have a mixed network of Deco M5 units and Deco M9s.
The main Deco is one of the M9s on the ground floor, on the first floor I have another M9, and then in the attic I have an M5.
For a long time the set-up has been perfect, with an expected chain where the attic M5 connects to the 1st floor M9 which in turn connects to the main M9.
Yesterday I upgraded the M9 to the lastest firmware: 1.3.0 Build 20190821 Rel. 54023
Now the attic M5 (fireware remaining at 1.4.4 Build 20200221 Rel. 65392) appears to connect only to the ground floor M9 via a very weak signal and hence now have terrible bandwidth in the attic. I believe this is the case because the app shows the attic M5 as "Signal Source" as the ground floor M9.
Anyone else experiencing a similar issue? Any ideas how to fix it?