@Shigeru_Lloyd 

In theory, if Satellite Deco can't connect to Main Deco, it'll try to connect to another Satellite Deco.

I wonder if something is up with new M4 you bought. Try this:

1. Place 'new' M4 side by side with second unit on first floor;

2. Power off second unit. Verify in Deco app that 'new' M4 is connected to Main Deco;

3. Take second unit which is on first floor and place it on second floor. Power it on there;

4. See if your 'old' second unit, now on the second floor, can connect from there to either Main Deco or to 'new' M4 which is on the first floor.

Let me know the result.

  @Alexandre. Thanks for the feedback.

I tried your suggestion, but when I switched unit 2 and unit, everything want red light. So I switched them back in their intended place and left them to their own device. After an hour or so, unit 2 was back on line. The next day, Unit 3 decided to finally connect to unit 2 to get the wifi signal.

so it seems that a bit of patience was all that was needed. It works a treat now, covering the areas I needed covered.

  @Shigeru_Lloyd 

I also facing exact the same problem you encoutered. Also try by my luck to make 3rd floor unit connect to 2nd floor units by reseting the 3rd units. Sometimes 3rd floor unit directly connect to main unit (ground floor), that will resulting poor signal. i wonder is there any function like asking which DECO to connect to which DECO manually.