iPhone calendar sending the same invite multiple times per day

I sent an invite to my partner and I a weekish ago. Since then, the invite has been sent to us many times, multiple times daily. I just took a look and

today by 9:30 AM: 5 duplicates in one recipients calendar

yesterday: 5

day before: four

before: one

before: six

before: 2

before: one

email sent from calendar app to external email addresses.

iOS 18.0.1 (22A3370)

iPhone 14 Pro Max