We found a bug in one of our projects that was caused by a pure function being evaluated twice when spawning an actor. I have been able to replicate it in a blank project like so:
Furthermore, the second time the pure function is run, the actor appears to already be in the scene (in first position evaluated), but then gets moved to second evaluated position! (this BP only proves that actor in scene for second evaluation, but this behaviour is what was causing a bug for us)