Here in Helaman 6:38, the printer’s manuscript had only a single that, namely, after the transitional phrase “on the other hand” (the original manuscript is not extant here). The 1840 edition supplied an additional that before “on the other hand”, probably because of the high expectancy of that immediately after “it came to pass”. The insertion was probably unintended.
There is only one other example of “it came to pass” co-occurring with “on the other hand”. In that instance, that precedes “on the other hand”:
In neither case, we should note, is the that repeated; it occurs either before or after “on the other hand”. But it is worth noting that in theory the that could have been repeated here in Helaman 6:38, as in the following example involving the prepositional phrase “on the morrow”:
For the use of the repeated that in the original text, see the discussion under that in volume 3.
Summary: Maintain in Helaman 6:38 the placement of the subordinate conjunction that after “on the other hand”; in the earliest text for this passage, there was no that before that phrase.