I'm hoping someone can help (I've logged a ticket, but no feedback yet). I've been through the forums, but unfortunately can't see the same type of problem.

Topology
Modem <-wired-> Main Deco M4 <-wired-> Switch <-wired-> [Various Devices e.g Storage]
                                                     <-wireless-> Slave Deco M4 (Kitchen)
                                                     <-wireless-> Slave Deco M4 (Bedroom)
                             
Installation
1. I was able to install the units as per instruction, without any problems.
2. The units were in a healthy state (solid white LED).

Problem
1. I noticed that all the wireless devices in the house only connect to the Main Deco. The impact is obviously that devices further away have slower speeds.
2. I confirmed this by logging into Main Deco web UI, and viewing the clients connected to the units under "Clients".
3. When standing next to one of the Slave Deco units the wifi signal indicates the strength of the Main Deco unit, but I noted that there is a strong signal for a hidden network.

Troubleshoot 1
1. I rebooted the Main Deco, hoping this would "force" the devices to connect to the Slave Deco units.
2. The Main Deco started up, but went into an error state (solid red LED).
3. The 2 Slave Deco units also went into an error state (blinking red LED).
4. I was forced to hard reset the Main Deco, and restart the intallation.
5. I left the network for about 12 hours, hoping that devices will start roaming.
6. After 12 hours, all devices were still connected to the Main Deco unit.

Troubleshoot 2
1. I again rebooted the Main Deco unit, hoping for a different outcome.
2. Outcome, and resolution, was exactly the same as Troubleshoot 1.

Troubleshoot 3
1. I also tested by disconnecting the wired Switch from the Main Deco unit, but there was no improvement.

Troubleshoot 4
1. I also tested by toggling the "Fast Roaming"/"Beamforming" options, but there was no improvement.

Observations
1. I've noticed that the Slave Deco units tend to rename themselves back to "M4R" whenever they are restarted/rebooted.

Does anyone have any suggestions/ideas on how I can get devices to connect to the Slave units?

Thanks!