"It's just a replica."
Translation:velqa' 'oH neH.
velqa' neH 'oH doesn't mean It's just a replica. That English sentence means it's merely a replica, but Klingon neH after a noun means that the noun is not accompanied by other nouns. The Klingon sentence means it's a replica, but not other things as well.
To get It's merely a replica, you'd need to say velqa' 'oH neH. When neH follows a verb (or, in this case, a pronoun taking on verb-like properties), it means merely, which is the meaning we want.
So this sentence should be updated:
It's just a replica.
velqa' 'oH neH.