I tried "the Ferengi ship repairs itself" and the "Ferengi ship fixes itself," and neither translation was accepted. Is there an inherent error in either of these translations? If so, the verb tense shouldn't be an issue, so is it a problem with the form of "Ferengi' I chose to use, or something else?
tlhIngan Duj also uses "Klingon" as an adjective and that is done using a noun-noun compound. If it had been in the singular, verengan Duj, then "Ferengi ship" would have been fine. It's the plural that makes things confusing. Does the plural automatically mean the word can no longer apply adjectivally? That's common in English, but I'm not sure it is in Klingon.
Let's think about it with the word "child" since it has a distinct plural that does not end in -s. You can say that something is "a child seat" or "a child's seat" or a "children's seat", but you normally wouldn't say that something is a "children seat". I don't think that we have the same limitation in the Klingon and even with the plural it can be used as an attributive as well as a genitive or possessive.
But since you wouldn't use the plural adjectivally in English, how do you express that in English? Is it OK to substitute the singular and use it adjectivally in the English?
Perhaps one confusing thing is that in English, the plural of "the Ferengi" is "the Ferengi" -- i.e. it is "one Ferengi" and "two Ferengi", like "one sheep, two sheep" or "one deer, two deer".
In this case, the ship belongs to many Ferengi, so it's verenganpu' Duj "the ship of the (many) Ferengi", not verengan Duj "the ship of the (one) Ferengi".
verengan Duj would also be correct in the plural sense of "Ferengi", granted, since plural suffixes are optional.
Finally, note the spelling of verengan(pu') -- there's no n after the ng.