So I'll note that the existence of language files for EP4 is not an issue, when/if Russian is used there may be an issue with the language content being populated properly such as importing the products_description related field, but it shouldn't cause the reported issue.
On another note, for the site having the issue, do the other exports also have an issue? E.g. the product export or price listing?
Another question, when looking at the EP4 admin screen, what index does the English language have? It's in the info on the upper right area.
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