I've been trying to get a Bookings site up and running and ran into this snag. The user is given a choice of two locations they can choose from (which each have their own calendars that will be linked correctly once finished) and the start times for the appointment, they should go 9:30, 10:30, 11:30 etc.
I'm using my own calendar for testing purposes and noticed that when I have a separate item in my calendar, for instance at 10-11, the Bookings site will show that there is a slot available from 11 instead of 11:30. I have the duration for the appointment set to 1 hour.
As for availability I have one location set 9:30-12:30 and the other set to 9:30-10:30, 10:30-11:30, 11:30-12:30.
It is also showing the last appointment as running from 16:30, despite the last one being set to run from 14:30.