Yes, I don't know if it is the Finder itself, or so other part of the OS/kernel that is in fault, and NO, I don't know how to reproduce it because it is such a scary experience (happend two or three times if I remember correctly) that I don't even want to go explore it, since I never even received an automated acknowledgment email from apple for bug reports or dump posts or anything like that. One time, there was a directory deep inside the one that was beeng moved that had the same name as the top level (I don't know if this was related to the error though) and midway there was a useless error saying some error happened and half the files could not be found not in the source not destination.