I witnessed the same flaw, the soldiers remain as "unloading" the whole battle, not being possible to retreat nor attack
in spite of the enemy force is just one unit.
This error its very annoying not only because you lose an entire troop in the hands o a single unit but also because of, given the time needed to unload, its very easy for the enemy to leave a bunch of quick troops near his coasts to intercept every attempt of landing.