Been trying to think about this. Need to look at the language pack to see its settings as relates to the database along with the returned data associated with the plugin. Note that generally speaking, as written mb_split and the other mb_ functions only really comes into play when utf8 is involved.

Would need to trace down execution about what happens to the imported text to see what operation is truncating it. I have seen that Russian also has had a similar issue.

Does the same problem occur in the product description or is it only in the product and category names?