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That is correct. It happened to me too. One time. I will
not make that mistake again. (Eventually I was able to get
another copy of the missing file from a torrent.)

The problem should be corrected, but one can also exercise
responsibility in handling files. It is reasonable to
expect that you can't be playing a file (read access) and
writing a file (write access) from two different
applications without having some problem.

But in no case should MTT just delete its temporary file
and the target file.

- - -

It's a shame this isn't being actively developed. I really
like this program. The file deletion issue is easy to
avoid and that is the only problem I have ever had with
mp3tagtools. I have tagged thousands of mp3s with this.
It's a great tool.

Hopefully somebody will resume working on it and adding
new features.