Very interesting. I haven't had time to test this myself (GTAC was remoted in on Friday night) and won't until Wednesday, so it'd be good if you could tell GTAC you're not using ATPC but are seeing the bug.
Had another debug session tonight, looks like ATPC is a red herring. Instead, try disabling all the DCS Interference Events in radio 2 advanced settings (we only had Bluetooth enabled, but that was enough to cause the radio to get stuck) and rebooting the AP.