Transcoding FLAC files replaces original metadata with an old project, can't remove old tags

In the hope that the developers will see this, I've converted the thread into a bug thread, as your latest revelation points the finger rather better...

However I still don't know HOW to edit meta data in an Audition WAV file in a way that it is saved correctly in a FLAC export.  If anyone could explain that to me, I'd appreciate the help.

So, I found the issue for me:
Since I don't use either markers or meta data in Audition, I did not check the check-box "include markers and meta data" during saving/export forms. (since I did not want Audition to write wrong meta data into the files...) But obviously exactly that is causing to write some old, left over meta data into the files - and not just the FLAC files, but also the WAV files!

When activate that check box to include markers and meta data, the meta data saved in WAV and FLAC files are empty.

So, actually I don't think it is related with the FLAC Encoder at all, or all, but AUDITON ONLY causing this problem!
I opened a WAV-file I created in Audition (version 2024!) in Audacity. When opening the meta data edito in Audacity the wrong, old meta data is being shown there already - without any export into a FLAC file!
So the wrong meta data is already present in the WAV file Audition created!
In Audition I could not find the same meta data being shown anywhere though!
I therefore still think the problem is 100% Audition - in all versions since at least 2022!

Not sure why it's doing that, but FLAC is essentially an 'external' codec, and it might have something to do with version changes over time. The only place you can alter metadata in Audition is Window>metadata, but how exactly this works with FLAC isn't entirely straightforward. Whatever is stored appears to be accessible under XMP, and it's an integral part of the file structure. But be aware that FLAC encoding/decoding is included in libsndfile, and that is externally maintained. You might need to talk to libsndfile directly for more information about this. A good starting point is here - I believe he's quite friendly!