I've seen this behavior with Windows' built in compressed folders utility, so it looks like something to do with files being extracted from a compressed state to the desktop.
If I had to guess, Fences is trying to move the file as soon as it hits the desktop, but since the file probably isn't complete it is either locked or the next time a chunk of data is written to the file it *pops* back to the desktop. On my wife's laptop I could actually see the file go from the desktop, into the default fence and then back to the desktop. I wasn't using Extract to X though, I was just dragging files from a compressed zip onto the desktop.
Just my .02,