I had 4 tickets and 1 reservation I needed to add to my calendar, so I expected to use the file>>import workaround I've been using for some time now.
Using the exact same conditions for each booking:

The first booking sent two emails, with no attachment for me to import.

The second booking sent a meeting invitation, which when accepted was added to my calendar, just like I dreamed they all would.

Bookings 3, 4 and 5 all sent a single email, again with no attachment. What a nuisance.

I just don't want to even think about this function, I just want it to work in SOME consistent manner.