I’d have to double check in the specs, but I confirmed that the switch and WAP are compatible. The WAP581 doesn’t have a wall wart unfortunately.what is the spec for provided per port power draw limit ?
and the 581 is supposed to consume how much at what voltage ?you might swap ethernet cable or test a plug in wall wart if it has a power supply provided.
the only other thing i can think of is energy efficient ethernet is some how getting triggered, but if it is happening while you are doing something on wireless, then that is out.
Go into the local syslogs on the WAP and see if it is telling you about the drop/reconnect.