Hello, I have 3 pieces cAP ac - RBcAPGi-5acD2nd with 2,4 and 5GHz wifi.
The problem is this: after factory settings works normally at 5785GHz, the two wifi adapters choose the frequency for 1-2 minutes.
But when working in CAPs MAN system and when set higher frequencies than 5280GHz I have to wait 15-20 minutes to react access point and start broadcasting SSID.
If I choose a low frequency 5180, 5200 or 5220 no problem, wifi adapter starts immediately broadcast SSID immediately
Where the problem might be?

Search for topics DFS and Radar detection.

Any channels between 5250 MHz and 5720 MHz (channels from 50 to 144, both included) are subject to DFS ... meaning that AP has to check that frequency sub-band is not used by some radar (air-control, weather or military) ... which takes some time.

Ok thank you.
Is there a way to speed up, for example skip DFS or save selected? Or or with another setting?

Don't use frequencies that are used by radars, if you can.

See console command:
Just use your own country name, and you will see which frequencies have "dfs" next to them.

Is there a way to speed up, for example skip DFS or save selected? Or or with another setting?

It's illegal to skip DFS protocol and that one has to be performed on any channel which is declared to be DFS-infested (even if there's no radar signal present). As @Normis suggested, use channels which are not marked as DFS.