When the Raspberry Pi 3 came out, it had some issues with WiFi channel 13. Now it looks like this is repeating with the Zero W for some reason.
I'm seeing some really weird things here with both the 4.4.x and the 4.9.x firmware/kernel branches:
The Zero W won't connect to any WiFi running on channel 13. However, a channel scan does see networks on channel 13! What's even weirder is that it starts to work when I plug in a USB WiFi dongle. Raspbian will still use the internal WiFi in this case, it just looks like plugging in the USB dongle "activates" channel 13 for some reason. And before you ask, the regulatory region is correctly configured.
Does anyone else see something as weird as this?