calendar keeps sending me invitations to events already in my phone

I’ve added hotel and plane reservations for a trip I’ll be taking soon. All of a sudden I’m getting invitations to add these events to my calendar. Nothing has changed, not the date, the time or the location, but every day I’m getting 3-4 invitations.

And if I accept the invitations on one device, why aren’t the invitations syncing to my other devices? I’ll get the invitations on my iPhone and accept them. When I open my iPad and MacBook, those invitations are still waiting to be accepted.