I’ve tried your experiment and you’re right.
One of them follows the project key and the other doesn’t.
I’m not 100% sure about this. I checked the metadata in Wavelab and the file that doesn’t work with the project key seems to be an acid file. There is some extra data compared to the other one.
acid…
After that there are attributes which are same for both files and contain the Cubase mediabay key,tempo…
After deleting the “flag1” attributes both files work with the project key.
Yes, you can process metadata in a batch, but while adding id3 tags (title, artist…)to several files at once is relatively straightforward, messing with xml is not.