I have a mix of 3x X60 and 4x P9. X60 is the main unit. All was fine when setup, but sometime last year all the satellites started showing offline - although they still seem to work. X60 satellites sometimes green, sometimes red. P9s nearly always white. 
 

When it happened I tried various things. Checked firmware versions (when I could get them connected). Reset every unit and re added them, even as I was adding them, others dropped off and turned offline on the app map. They setup a custom connection map at the time, but now all are as a star and showing offline again. Reset all again and set them up again with the same results. To be clear, I'm currently looking at the living room satellite X60 which is probably the furthest away from the main unit and it's green and working ok. There's another almost directly under the main unit showing red, it was green yesterday. Even when showing green they appear red in the app map. 
 

Connected to a virgin media fibre hub 4 which I've also reset. Deco X60 used as gateway / DHCP

It looks like there may be a new firmware upgrade since I last played with it, but it won't update because not all my units are online.