Complex sentence: As the number of swivel casters attached to a wagon increases, though, it becomes increasingly difficult to align them, and it is difficult or impossible to move a wagon when its casters are unaligned.
Split into simpler sentences: As the number of swivel casters attached to a wagon increases, though, it becomes increasingly difficult to align them. Consequently, it may be difficult or impossible to move a wagon that has a large number of casters when the casters are unaligned.