The earliest text reads “in this your ways of sin”. The use of the singular this with the plural ways is probably the reason why ways was replaced with way in the 1837 edition. As explained under Mosiah 7:23, the use of this with plural nouns occasionally occurs in the earliest text. Moreover, there is more than one way of sinning, so the plural “your ways of sin” will work. In fact, there is one other instance in the text of “way(s) of sin”, and that too reads in the plural:
The critical text will therefore restore the original plural ways in Helaman 9:21.
Summary: Restore in Helaman 9:21 the plural ways in the phrase “in this your ways of sin”, the reading of the earliest text, which is also supported by the plural phraseology “the ways of sin” in Mosiah 16:5.