Avoid duplicate import entries

I have a Multiterm termbase that consists of English and eight other languages. I now need to add a ninth language by adding the language to the definition. After doing this I create a new import definition file that synchronizes on terms. However, no matter what I do and what advanced synchronization options I select, I do not get the result I want, which is one entry per language. The English from the new import file always seems to duplicate in the termbase, no matter what I try.

I am converting a bilingual Excel document, English and Danish, to import. In case that matters.

I seem to be getting results like: 1 English entry, removes the other language entries and inserts the Danish, or the most common, with the majority of options I have tried: 2 English entries. I need one entry per language and the English always seems to be duplicated.  I am trying to avoid duplicates, however nothing I do seems to work.

I have tried to synchronize using English and overwrite, merge, omit and add as new. With Source I have tried to overwrite, omit and merge. Danish, I tried to overwrite and add as new, and Target I tried to overwrite. I can try all of the other combinations, however these seemed like the most plausible.

Any help or advice would be much appreciated!