The odd circumstances aren't really relevant, though I admit they're a bit odd.
If you break up on good terms, I think it's healthy to stay friends. This person has valuable insight to who you were at a certain part of your life and unique perspectives.
You gotta be able to be respectful, though, both you and your ex. Don't weaponize the intimate knowledge you have with each other to score points with their friends.
At a convention, Tim Russ told a few stories about being a real prankster on set, so maybe he just got rebuked by his coworker for messing up a shot