Bookings offering random time slots for appointment

We have 3 services with time slots available from 8 am- 8pm but now have seen that on the Bookings page there are time slots available up until 12 am and slots that are available are not showing up. When you test and try to book at the times available you get a message that says "Someone beat you to it. This time is no longer available". I do not see availability settings that would cause this on any level in Bookings. Please let me know if there is something I can do as these appointments are critical. Thank you!!