Album art adjust action creating a second instance of same sized art?

[JohnIV]

I use the album art adjust action to transform my selected songs' album art to a standard size (600px).
I have noticed lately that after I have done this action it will appear that I have two album arts embedded in the song; when this happens both are 600px but sometimes different sizes leading me to believe the original was also 600px to start with.

What is the preferred method to prevent this duplication, is the album adjust smart enough to see if the target is the same dimensions before running?

[ohrenkino]

What kind of files are these?
Have you checked the files for integrity?
Because I cannot reproduce it with MP3 files.

[JohnIV]

These are VBR *.wma files, converted via fre:ac.

[ohrenkino]

I cannot say anything about that process.
But I would still check the files for integrity first e.g. with Foobar and then see whether further embedding of data leads to strange effects.