Phantom Volumes Created by Motion

I had an interesting issue occur that I didn't realize was happening until I ran out of startup hard drive space. I set my autosave vault and my retiming cache preferences to an external hard drive and set it to a specific folder. I thought that was all I had to do to make sure the files were being rendered out to them but for some reason I have a new folder on my startup drive that is listed as Autosave Vault and in it I found several files that I thought were going to the volume I had already specified. When I went to the internal hard drive to find them however the volume is not listed but is taking up real hard drive space. Most of the file space is taken up with .mv files but they are impossible to locate in a spot outside of the Motion Prefernces window where they can't be deleted. Short of dumping my entire Start-up drive and starting fresh has anyone else run into this issue or have you even realized this is happening. I hadn't realized it until today when I ran out of drive space.