When you are not using an API connection, but just iCal calendar feeds, OwnerRez creates bookings and blocks based on imported data send to us in the iCal calendar feeds you've imported. When a new event appears in the calendar feed that we haven't seen before, we create a booking; when that event disappears from the feed, we cancel it.
Unfortunately, the various listing channels tend to create events in the calendar feed that aren't really bookings. For example, when a guest starts through the booking process, the dates they've selected will be blocked off, even though they haven't completed the booking process and made a real booking. This makes a certain amount of sense, since you wouldn't want two people booking the same dates at the same time.
However, because of the way the iCal standard works, this leads to the kind of whiplash you're seeing, as "bookings" bounce in and out of existence.
To prevent this, where possible, OwnerRez tries to identify what's a real booking and what isn't. That's why we recommend using the setting to import "Bookings Only", not "All Events". This generally solves this problem.
Unfortunately, we can only do this if the channel provides some sort of status flag in the calendar feed from which we can determine which events really are bookings and which aren't. VRBO does. Airbnb also does, but it's not completely reliable. Currently, it looks like Booking.com does not.
This is one major reason why we recommend to use API connections wherever possible - they don't have this problem.
