Question about UniFi AP AC-PRO - 147022

I own this model and the Long Range. For about 2 months I have had problems with all Android smartphones and 1 tablet in the house: Every now and then it takes 1..2 minutes for data to flow. For example, when I start the music programme Replaio, it takes 1 minute until the start screen of the app is displayed. After that, when I select a piece of music, it takes forever for the song to start. With the wifi analyse app cnlab analogue. Often, the first time I start the app after a break, the data transfer does not start at all. After 30 seconds the app shows me the result as 0 mbit/s. With repeated attempts it suddenly works and the data flows normally fast..90 mbit/s and ping times of 15ms. This phenomenon is with several devices (3..4 mobiles and 1 tablet). Everyone in the household has noticed that the network takes time to respond. With other routers and access points everything works fine. Resetting, re-adopting, new firmware, defining new ssid have done nothing. All Ubiquiti APs do not work. I have not found anything unusual in the control software, no ip collision, no interfering transmitters. Also on the swisscom router (internet box 2) everything seems to be ok. Does anyone have the same problem? Ah, one more thing, no computer (4 notebooks, 2 pc, ps4) in the house seems to be affected by the problem.