[BUG] A Yearly Repeated Event is shown twice

[Nurgotora]

Essential Pim 11.8
Window 11

A yearly repeated event (Starts in 2013) is shown twice in 2014 and all the years after. Deleting any of the two (as the whole series) deletes 'both'.

As usual, I've a cleaned epim database with only this event in it.

Fun fact: If you look closer, you'll notice that one of them (either the original or the the 'twin') increments the number in the brackets, but not both.
See also: [BUG or FEATURE] Yearly Repeated Events Increment Number In Brackets

[admin]

Can you reproduce the issue by creating a new recurring event?

[Nurgotora]

No. It happens arbitrarily.

But, as I said, I've a database with only this faulty event in it.

[admin]

Our assumption is that this event appeared due to synchronization with another device or service.

[Trinitylab]

I get this once awhile too, sync only FROM epim to anything else.

That is why, for years i haven't been using repeating events.
Total mess.