Oh wow. This is crazy to read it from a scientific point of view, but I am pretty sure that it has happened to me too!
Like you mentioned aswell, that some memories combine so maybe there were two different things but the brain just groups it together as one.
Sometimes I even have it with dreams. Just tiny details which i could think of and then I am actually note sure if that scene actually happened or if I only dreamt it.
Thanks for posting, I enjoyed it. Cheers!