Bookings is creating events on all staff assigned to that service instead of just booked staff?

I have created services and assigned staff to them. Currently I have it set so that customers have the option of choosing a staff member as we sometimes ask they choose a specific person. However, we don't always need them to choose someone in particular in which case I expect them to choose the "anyone" option. This if fine but for some reason if they don't select a person it books with one person according to the bookings calendar but then creates events on the calendars of everyone assigned to that service. Is there a solution to this problem? Basically, if they choose "anyone" I would like it to book with one staff member randomly and only add the calendar event to that person's calendar and not anyone else's.