Specific concept label not appearing under "Terms" section

Hi everyone,

while working on custom conjugations I noticed a rather strange behavior. I have set up a concept with several German concept labels:

Despite having a concept label for female, singular set up, it does not appear in the “Terms” menu - only the plural appears.

Even weirder, if I set the default concept label to female, singular it does appear in the preview, so it seems like it is being saved somewhere.

I have tried hard reloading, but this does not change anything.

Any ideas?