Replacing an XT8 main node (AP mode) with a ROG Rapture GT-AX11000 Pro: is worth?

[kildare]

Hi, I have a large 3 floor building with concrete/brick internal walls, and a mesh network (AP mode) consisting in a main XT8 and 5 XT8s, 3 of them are connected via a 2.5 GBe ethernet backhaul, 2 connected via the 5GHz-2 backhaul.
Now running latest firmware v. 3.0.0.4.388.23285 (anyway tested many others in the past, included latest gnuton's).
No problems at all with the 3 wired XT8s.

The problem:
after a mesh reboots (even by power off/on), the 2 wireless connected XT8s show a "Great" backhaul, and stay so for a couple of days, meaning that the 5GHz connection is possible and good.
The wifi backhaul is established directly with the main XT8.
But after then they consistently (and repeatedely) switch to a 2.4 GHz backahaul indicated as "Weak" in the GUI.
For these 2 wireless connected XT8s I also tried to set one of the other wired XT8s as their "Preferred WiFi Uplink AP", but this setting is apparently ignored and they always reconnect to the main node.
Do you think I could get an improvement and a solution to this issue replacing my XT8 main node with a ROG Rapture GT-AX11000 Pro?
Thanks.

 

[L&LD]

How big is this building in SqFt? Are the floors also concrete? What is the SqFt of each floor?

How far are the wireless nodes from the main router? Can't you simply place them closer?

Can you shuffle/relocate the existing, wired, router/nodes to get the coverage needed, without using the two additional wireless nodes?

Have you set up the network from a freshly reset to factory defaults main router, without using any backup config files, and with a minimal and manual configuration? And when the main router was fully set up, adding the nodes after they were fully reset too?

Have you tried different control channels (manually, for at least 24 hours or more)?

I'm sure nobody can answer you confidently that a new router will solve all your issues, but if you haven't set up your current network properly, you are just trying to solve things by throwing money at the issues (and that rarely turns out well).

 

[kildare]

3 floors of 100 square meters each.

One of the locations of the XT8 with the wireless backhaul problem is shown in the image