Devices not connecting to 5g even being 1ft away from router

Hello everyone,

my main problem is stated on the subject: my devices are not connecting to 5g even being 1ft away from router/satellite, on the same room, no blocking objects.

When I try to change to 2g/5g channels sometimes the capable devices will connect to 5g (and work well) but then at some point soon they go back to 2g and my speed problems are back.

Also, sometimes the devices are not connected to the router/satellite near them. Again, talking about 1-3ft distances. I'm relying on the connected devices list on the admin section, but I'm not 100% sure it's 100% reliable.

My system is a RBR20, 1 router and 2 satellites. The router is on top floor and the satellites are wired connected on 2 bedrooms on the floor below the router. The satellites are around 30ft far from each other, with several concrete walls between them.

System firmware is V2.7.3.22 . The modem I use is on bridge mode, so the Orbi is my unique wifi system. There are 20+ others wifi networks around.

Except from phones, I don't walk around too much with the devices, so if we had 2 different networks for 2g/5g my problem should be gone, but I gave up on going through that route as all suggested ways that I saw didn't work for me.

What could I do to solve these issues?

thank in advance