Use Case: Top Chef Teaches Cooking. They can either teach Chinese cooking, or Indian cooking. In either case they have a class limit of 12. Availability 1 - Indian Kitchen Availability 2 - Chinese Kitchen Event 1, Indian Cookery requires an Indian Kitchen Setup Event 2, Chinese Cookery requires a Chinese Kitchen Setup Each should be bookable up to the maximum number, but they can't teach both at the same time. It seems to me that this should be solvable by simply adding a Top Chef calendar to both availabilities, and this is how I would have expected it to work. Current Behaviour: Top Chef can book out their calendar (eg for Top Chef Date Night With Their Beautiful Partner), and this prevents EAB from booking an appointment into that slot. The first EAB appointment in any particular slot is bookable as it should be, however an appointment attached to a different availability can also be booked into that slot on the calendar.