I have the same problem. The area of the wifi signal is not so good. Additionally my phone (with Android 10) connects everytime to the 2,4G network and reconnect sometimes. The SSID of the 2,4G and 5G networks is the same. I didn't had these problems with an unifi AP.
there is a new eeprom. Will this change anything?: http://www.minihere.com/newifi3-d2-eeprom-download.html