You can enter up to the last minute of the designated hours, no problem. If you exit after designated hours, you cannot check-out. You can leave any time you like, but you cannot check-out. (Call it the Hotel Anti-California.)
If you hit the call button to ask the after-hours staff about this problem, loud alarms go off. No one answers, and after a short interval the alarms stop. No one arrives to investigate.
If you then phone the after-hours staff, they tell you that since the alarms have stopped, there's no problem they can fix. (They will be glad to turn off the alarms, if you need that.) They say that if you are unable to check-out, staff will simply think you're still inside, and that you can straighten that out during business hours.
Another irritating thing to deal with in the morning.