On the 5 GHz, if you manually set the frequency, which I recommend, be aware that if you select a DFS frequency and the device senses a RADAR signal on that frequency, the device is required to move to a different frequency. So, if you see your device has moved from what you set, that could be the reason.
Mounting of WAP's is a real deal-breaker I see daily when I am brought in to fix crappy systems. UniFi suacer WAP's throw a wide cone of coverage and should not be on walls, put on ceiling where they are supposed to be. If you need to use a wall, then get a WAP that "Stands Up" like AC-M or the Outdoor AC Pro. New WAP's like the U6 drink cans also work. The other Golden rule with Ubiquiti: AUTO is EVIL
