Here is an example I just found. I was looking at Abraham Kornelius Fast, who lived at Sparrau #22 in the census. His entry says that he transferred from the Neukirch village (underlined in red) in 1830.
Then I checked the original Russian for Neukirch village, and I found him at Neukirch #23. "Abraham Korneliusov Fast" is underlined in blue and "Sparrau" in red.
What had happened? Why wasn't he in the English? When at looked at the English translation for Neukirch #23, he was there; but the name was mistranslated at Voth not Fast. This is an easy mistake to make because Voth in Russian is Фотъ while Fast in Russian is Фасть. The two names look quite similar in Russian, and if you're dealing with a poor microfilm copy. . . .
[A sharp-eyed reader might notice that the Sparrau entry says he moved to that village in 1830 while the Neukirch entry says that he moved away from that village in 1833. That discrepancy is in the original. It may have arisen because people often physically moved from one village to another but it took time for their legal registration to be transferred.]