theres th thing for this- every time you recount a sequence of events you remember the previous telling rather than the first account direct. Why it's important to take first hand accounts as close to the event timewise as more reliable. But not always.
*wavey hands* the brain is a pattern matcher, its what its for, half tthe shit we get fed in from the senses is filtered out and best-guess filled in based oon incredibly complex pattern matching routines.
I'm about to have a spliff so might get even more waffle hand wavey 'look at it man, really, look deep' later.