The clients are students with Laptops that are a mix of brands and operating systems. I know that one is an HP and another is a Toshiba. At least two are running Atheros wireless cards (I don't recall exactly which card or driver revision). We have seen the issue on laptops running Windows 7, 8.1, and 10.
On the 5Ghz the power has a min of 3 and a max of 12. The 2.4 has a min of 9 and a max of 15. Client match is turned on for both radios.
We first noticed the issue on August 22nd. We have been seeing the issue for a couple weeks. When the issue first occured we thought it was one isolated client but we have now seen several cases.