In Helaman 3, Mormon focused on the movement of Nephite dissenters, as well as some of the Ammonites, into the land northward. In Helaman 4, he notes that there was also dissension in the church and that “the rebellious part” were either killed or went south to the Lamanites.
The Nephite nation is being put under increasing pressure, pressure that will build between now and the time of Christ’s appearance. One of the important aspects of this pressure is that there are again “many dissensions in the church.” That phrase typically has meant that there are those in the church who have accepted the desires for social hierarchy. For some, the top of that hierarchy was a monarch, but from a historical perspective it was probably driven by the influence of surrounding cultures. Those cultures had wealth, and the wealthy had power. Monarchy or not, there was a social stratification.
While not stated, it would not be surprising that one of the dissensions in the church was once again the denial of the coming Messiah. That is, perhaps, the most consistent Nephite religious apostasy.