It sounds an awful lot like php's unlinking call.
PHP: unlink - Manual
The file gets deleted, but it still has handles pointing to it so it can't be overwritten.
I don't think this helps, because none of my code is using the unlink command.
PHP: unlink - Manual
Quote
On Windows, it is now possible to unlink() files with handles in use, while formerly that would fail. However, it is still not possible to re-create the unlinked file, until all handles to it have been closed.I think this seems consistent with what I'm seeing.
The file gets deleted, but it still has handles pointing to it so it can't be overwritten.
I don't think this helps, because none of my code is using the unlink command.