My BF does sometimes have several versions of an event. It's just the way each of him sees what goes on. If there's enough emotion involved, he can even have "false" memories where flashbacks of past events get confused with today. d'you know how it so hard for the cops to get matching eye-witness testimony? Because everybody perceives something different? In a way, he lives with that every day. More than one account of what happened and memories that fade in and out.

He's not lying. Not consciously choosing to speak untrue. It's just that his reality is fluid.