Due to some systems like VMS, the "sanctioned" idiom for deleting files is like:

1 while unlink($filename);
[download]

Or variantly,

unlink($filename) while -f $filename;
[download]

However, that kind of loop appears a bit dangerous if you're not sure that unlink() will always eventually return FALSE or remove all versions of that file.

It SOUNDS like that's the kind of bug the -C cleanup code is introducing here. If the file is still open, then going into one of those loops would have the behavior you're experiencing. I haven't dug into pp's code, though, to be sure of it.