In this verse, the 1874 RLDS edition replaced the second occurrence of the plural records with the singular record. In this passage, either occurrence of records could read in the singular. Thus there seems to be no particular motivation for the change in the RLDS text, which suggests that the singular record is simply a typo. The third RLDS edition (in 1908) restored the original plural, apparently by reference to the printer’s manuscript.
As discussed under 1 Nephi 5:21, the Book of Mormon text has considerable variation between the singular record and the plural records. Moreover, either number can be used to refer to one specific record. For instance, here in Mosiah 22:14, the second occurrence of records refers to the record of the people of Jared (that is, the 24 gold plates of Ether). The text elsewhere in the book of Mosiah uses both the singular and the plural to refer to this particular record, although most instances are in the plural:
Notice in the last example how the singular pronoun it is used to refer to the plural these records. Variation in number for record(s) is clearly possible. Thus for each case of record(s), the critical text will follow the reading of the earliest textual sources in determining the number.
Summary: Maintain in Mosiah 22:14 both occurrences of the plural records (the reading of the earliest textual sources).