It's a severe problem
Lower-level translators (those who can cope with ILR 2 or 2+ texts) have a serious problem with Russian grammatical endings. They ignore them.
What do I mean, and why is this a problem?
First, Russian has a fairly rich system of grammatical endings - six cases by anybody's definition and three genders. (I say "six by anybody's definition" because there's a special locative which is different from the prepositional, a remnant of a time when they were separate, and also a partitive genitive with different endings.) This rich system permits Russian a highly flexible word order. Sentences beginning with predicates and ending with subjects are very common; they express emotion and focus, as well as serving the ends of information structuring.
For instance, the sentence обоих мог убить один и тот же киллер. This is a quite ordinary sentence, but it does have an emphatic word order, leading into speculation about the killer's identity and previous actions - and it leads with the direct object:
обоих (both/masculine/accusative) мог (can/masculine/past tense) убить (kill/infinitive) один (one/masculine/singular/nominative) и (and) тот же (lit: this indeed (the same)/masculine/nominative) киллер (killer/masculine/nominative)Thus, this sentence could be translated in a number of ways, the simplest of which ignores all the information conveyed by the word order: one and the same killer might have killed both men. Or, using an English focusing device: it might have been one and the same killer who killed both men. Or, using the English passive to mirror the sentence most closely: both men might have been killed by one and the same killer.
But this is how it was translated by three of my students today: "both could kill one and the same killer".
The endings were just totally ignored, and the sentence was translated linearly. The words are in the same order, but the meaning is completely reversed.
Now, at level 2, Russian prose is pretty much Subject-Verb-Object. Thus, people who deal primarily with that level of prose become used to that structure, and are lulled into thinking that Russian's grammatical morphology is probably a baroque frill. After all, English gets by without it.
The trouble comes when they venture beyond newspaper and other reporting, into the world of writers who use every tool at the disposal to craft sentences which convey as much by nuance and implication as by direct statement. At this level, the endings of Russian carry critical information, crucial to understanding. Junior translators cannot accurately translate what they do not understand.
Remedial training in Russian grammar is often resisted by people who've been working for several years, but it's all too necessary.