when attempting to delete a list of FeedItems I'm getting the following error:
EXCEPTION: System.DmlException: Delete failed.
First exception on row 1 with id 0D5G000000h9c6ZKAQ; first error:
DUPLICATE_VALUE, duplicate value found: <unknown> duplicates value on record with id: <unknown>: 
As I understand it the DUPLICATE_VALUE error is for then you try an insert/update/upsert and you have a duplicated value in a unique field, I don't understand why is this firing on a DELETE operation.
I checked and don't have duplicate FeedItems in the list, I even tried doing:
List<FeedItem> fiList = [SELECT Id FROM FeedItem WHERE Id in ('id1', 'id2')]; delete fiList;
and I'm still getting the same error.
I have just one trigger and I alredy tried disabling it and the error still happens.
The error doesn't happen always, but I can't find any logic to why is happenning.
Any ideas of why this may be happening or how to fix it will be greatly appreciated.