For me, 3 phone calls to web support and over an hour was the only way I could cancel check in on a flight in early April.

I wanted to do it again for a return flight with my SO, where it wouldn't let us on the airport upgrade standby list, as it performed auto-check in for us even though I never even saw the option on the kiosk on my outbound. Along with bringing back the cancel check in button, perhaps we can remove the auto-check in option