In 1.00(AAKL.28)C0 Sideband control doesn't work. Can't use Wifi Auto channel if any of your devices doesn't support channels 12-13.
Its never recommended to use Auto anyway, especially on 2.4Ghz. Due to the lack of consistency in devices in the UK supporting 12-13, you want to stick to channels 1, 6 and 11 to avoid clashing with multiple channels. Auto has a nasty habit of picking other channels, causing crosstalk that other devices can't see.
WiFi relies on being able to SEE when any APs you are on the same channel as are transmitting, you need to be on EXACTLY the same channel for that to work, otherwise its just seen as noise and impairs performance. Not an issue if you have a clear channel to yourself, but that's only going to happen if you live in the middle of nowhere with no neighbors on 2.4Ghz and increasing rare even on 5Ghz.