Multiterm 2019 - Cannot save entry

I created a Termbase on SDL Multiterm 2019 and wanted to add a term that is the same in English and the target language (Portuguese). The reason I wanted to create it is that it's a 3-word name of a product, with Trademark symbol, etc so I thought that, by creating an entry in a Termbase, it would help me to type it faster and prevent errors. However, when I try to add it, I get the following message:

Cannot save entry. Equal synonyms in the same index within the same entry are not allowed.

And there's nothing else I can do. Is that really a limitation or am I doing something wrong.

TIA

Fernando Domeniconi