Meaning of message in failure report after on demand erase


When I do an on demand erase of saved tasks, some files are shown as "Failures", where only a few have the explanation shown after the path & file name:

<b>Cannot create a file when that file already exists.</b>

What does that mean? In some cases the files named do exist, at least before I reboot. In one case, after erasing (when the report from Eraser pops up), one file listed as a failure w/ this reason, did not seem to exist.

I think that all the files listed as failures wind up getting erased on reboot, but I'm curious what the message means.