Seems like BB can't count consistently or the code logic, quality and testing is pretty dire.
I can get up to 2 from the Event Shop which would give me a total of 10. I know of other players that can only get 1 even though that would take their totals to only 8 or 9.
And of course it would help if instead of saying 3 per event, the Dev Diary said up to 3 per event to a max limit of xx - and then applied this logic consistently.