Collective-booking event not added to all staff calendars

Collective-booking event not added to all staff calendars

We assign two staff to certain events. When the client books this event, it adds it to one staff calendar (the 'organiser') but not the other. How can I ensure all staff assigned to a collective booking get the event in their calendar?

(A side note: it appears the 'organiser' role is assigned to the staff member you click first when assigning a group, which is easy to overlook.)