Going on a date/initial meet with somebody that ended up being a mutual with another partner, and later a DIFFERENT partner.

Then some weird jealousy and blaming and emotions and multiple weeks of feeling like a terrible person until I talked to the mutual partner and realized they had warped the entire situation.

I wasn't even into that person and it blew up like six relationships. And I consider myself and try to be a patient and fair person, proactively on the lookout for stuff like that.