ical default calendar for incoming invitations

Having some trouble with invites that I receive. Even though I have my default calendar set in Preferences to Work, incoming invitations that are coming through from email and icloud (I receive an email from icloud and I have a pending invitie in Calendar) it insists on placing this in the US Holidays calendar when I accept this.

Since you can't choose your calendar when you're accpeting and it's not using the default calendar preference, I then have to go into each one and change it every time.

US Holidays is last in the list so it's not just choosing the first one so I'm not sure how the Calendar app chooses a default on its own.

Any ideas?