Wow, amazing write up and solid deduction! Tnx! sounds totally logical, seems to be what is happening indeed. It's more like a star or "hub and spoke" topology in it's preference, than to a mesh, as...

same issue here with M9 +, doesn't make sense and needs to be fixed.

same problem here, doesn't make sense. TPLink please add option to manually select signal source, and/or fix the algorithms

I have the same issue. It doesn't make sense to me. It seems that "slave" Deco's try to prioritize on the base-station, and even with a low signal try to connect to it as their signal source, even...

Same issue here with a Deco M9 Plus tri-pack. This doesn't make sense at all? I've got 3 levels: living room ground floor, bedroom, attic. I've installed in order from bottom to top. Now the attic...