The 1837 edition replaced the preposition upon with on (accidentally, it would seem). The Book of Mormon text definitely prefers the preposition upon when referring to the act of engraving (up)on plates. Even so, all but three of the examples with upon are found in the small plates of Nephi. In fact, the small plates have no examples with on, only 23 examples with upon:
the small plates of Nephi
“to engrave(n) upon plates” 23 times
“to engrave(n) on plates” 0 times
Elsewhere the usage is almost evenly divided between upon and on (here I include Mosiah 28:11):
Mormon’s abridgment of the large plates of Nephi
“to engrave(n) upon plates” 3 times
“to engrave(n) on plates” 5 times
Since either upon or on is possible with the verb engrave(n), the critical text will in each case follow the earliest reading (thus upon here in Mosiah 28:11).
There are four preceding occurrences of “engraven on plates” in the book of Mosiah, which may explain why the 1837 compositor set on in Mosiah 28:11 instead of the original upon:
Except for the preposition on, the first three read precisely the same as in Mosiah 28:11; thus the change to on in Mosiah 28:11 is not surprising. The 1837 compositor made the same error of changing upon to on in one other place:
The 1908 RLDS edition restored the original upon in Mormon 1:4 but not in Mosiah 28:11. Of course, upon itself is archaic for modern English speakers, which may be another reason the 1837 compositor accidentally replaced upon with on in Mosiah 28:11 and Mormon 1:4.
Summary: Restore the original preposition upon in Mosiah 28:11 (“the records which were engraven upon the plates of brass”), similarly for Mormon 1:4 (“ye shall engrave upon the plates of Nephi”).