"Let's confirm Thursday. (Later...) OK, let's reschedule for Monday. (Later...) OK, let's reschedule for Wednesday. (Later...2 hours before interview...) So sorry, the job was filled with former employee." Maybe interview your former employees first before dragging out everyone's time/efforts while you negotiate salary and benefits with your first choice former employee.
I would say every project has ambiguity. I have yet to come across a project without ambiguity. That said, leveraging your team members and ensuring to ask probing questions will assist in clarifying situations and provide more clarity.