@Nate_Spain 

If one unit is turning red, move it closer to either of the two Deco units as it may be losing a wireless connection which will turn red.

If the entire Deco system is turning red, swap the satellite M4 with the main M4 to see if the current main Deco is causing it.

It might be worth examining the modem when you notice this issue to see if the LED lights change.

@Tony  

I'm going to try swapping the nodes.   If it's a distance challenge it becomes an issue.  I've then got the 2 M4 nodes essentially on top of each other.  In a 100 sqm house I've have them at one end of the house within 2.5 - 3 M.  I'd need a node in every room of a relatively small flat.

I almost always check the modem when they go red.  Nothing unusual there.  What still makes no sense is what happened last night again.  The main node goes red, I'm still getting internet in the main room but the bandwidth drops, secondary node is still white and running fine.