Ooops, while searching anew for the same reason, I found my own ancient post here.
I did now my promised homework and finished the translation of all untranslated strings, while searching and replacing the 'translated' string in question which still was shown in English untranslated.
Hope, now everything works fine.
Btw: what does "unreviewed" mean? Couldn't find to mark as reviewed those already translated strings to finish the process…