Why do your duration slots disappear after just one reservation when you have availability?
The reason your durations disappear after just one reservation is most likely due to your packages "staff capacity" for the day being set to 1.
Staff capacity is how many reservations your staff can handle setting up at the same time, or essentially, how many reservations can be reserved per duration.
For example, if your staff capacity = 1, only one reservation can made per time slot. (Ex: if someone reserved a time at 10:30am, no one else can reserve at 10:30am). If your staff capacity = 2, 2 reservations can be made per time slot.
So change your staff capacity to the number of reservations you are comfortable with your staff handing at the same time for this specific package!