There is a problem with the new late joining mechanics when you are on a ship that is boarded. Because the enemy goes first, if anyone joins the battle they are counted as not coming in on the first turn, even though the one on the ship has not had a turn yet.
Add to this the fact that the number of added enemies was not correct. We had three players and three companions against eleven enemies. If there were only one enemy added per late joining player, nine enemies in a battle against one player is not right, but eleven against three with companions is about right.