mk63 5Ghz connectivity issues

hey there, is there any way to force 5Ghz connection? I've recently purchased and connected Nighthawk MK63 and the current setup is that the router is connected to the internet provider (1gbit) at the groud floor, one satellite is at the first floor and second satellite is at the second floor. All is connected through backhaul link using a gigabit switch between router and both satellites. 

The setup worked fine until last week ... and since last weekend all my devices (PS5, phone, laptop, etc.) connect only to 2.4Ghz channel (both 2.4GHz and 5Ghz use same SSID). I cannot force switching them to 5Ghz channel even if the device is very close to the router or satellite.

• Is there any certain procedure(sequence) how the router and satellites shoud be relaunched (after e.g. electricity outage or something) to work in sync with the router using 5Ghz channel?
• Is there anyone having same issues with 5Ghz channel using MK63? 

Synchronization between router and satellites does not help at all, I did that several times. I believe that the full factory reset of the router and satellites may help, but come on, this should not work like that...

Cheers.

The setup is as simple as that.