Isaiah 29:10 (King James Bible) the seers hath he covered
The 1830 edition accidentally replaced the singular iniquity with the plural iniquities. The earliest text reads in the singular: “because of your iniquity”. The 1837 edition restored the original singular, probably by reference to the printer’s manuscript.
The prepositional phrase “because of your iniquity” is not found in the corresponding King James text (probably because much of this passage paraphrases Isaiah 29). Elsewhere in the Book of Mormon, we have instances of both the singular and plural in referring to “one’s iniquity/ iniquities”, with the plural occurring nearly two-thirds of the time (for the statistics, see 2 Nephi 4:17). In each case, we therefore allow the earliest textual sources to determine the number.
Summary: Maintain the singular iniquity in 2 Nephi 27:5 (“because of your iniquity”), the reading of the earliest textual source (here the printer’s manuscript).