I found a solution, 1. in the deco app click on the globe icon (says internet) 2. click on the three dots column in the top right - select "Set Main Deco" 3. Choose the main deco to be the unit in...

I have the same problem. Remote unit connects to the far-away main unit directly instead of another in-between unit. I'm on Deco M4 but the issue is exactly the same.