Here the 1874 RLDS edition changed the plural persecutions to the singular persecution, unintentionally it would appear. The 1908 RLDS edition restored the plural reading, probably by reference to 𝓟. Elsewhere the text has 11 instances of the plural persecutions and 4 of the singular persecution, yet there has been a clear tendency in the history of the text to replace the plural with the singular, as in these three additional examples:
The critical text will follow in each case the evidence from the earliest textual sources in determining whether persecution should be in the singular or plural.
Summary: Maintain in Mosiah 27:3 the original plural persecutions (“that there should be no persecutions among them”), the reading of the earliest textual sources.