Some Events Not Syncing With All Apps

I had a meeting series invitation arrive late yesterday and that hasn't appeared in Mac Calendar. I've tried restarting calaccessd, refreshing calendars from Outlook and Calendar, but nothing changes. I can create events, both single and series from both sides, with Exchange and Google calendars and they're all copied across. I can't see anything different about that invitation. I've disabled and re-enabled the Exchange account again and all events are now showing, including the one that previously wouldn't sync. I've seen suggestions of clearing potentially corrupt calendar cache, but I don't see the files they suggest to delete.