I had a repeater connection to an upstream router on channel 116 and wireless 5g setting on.
after a reboot the slate connected quite quick to upstream router, however the internet connection page displays connecting even though it is connected.
The wireless page still says checking for channel availability at the time of writing this when uptime is 35 minutes.
I connected successfully on this channel yesterday from slate to an upstream Asus 88ax router.
Edit: The Slate AX access point is not available so it is not just an interface issue.