Thank you very much for your quick answer. Indeed, manually setting the frequency outside the DFS band caused the 5 GHz network to start immediately. Following your hint, I found an article, where there is a description of the DFS mechanism: http://wifinigel.blogspot.com/2018/05/the-5ghz-problem-for...

Hello, everyone, I have hAP ac2. When I start it or restart it, the 2.4 GHz network starts without any particular delay, while for the 5 GHz network I have to wait 10-12 minutes. Once the 5 GHz network starts up, it works quite stable. Is it normal for 5GHz to start up about 10 minutes? I'd apprecia...