This deals with ships that wish to retreat to harbor and may not be able to.
It seems clear to me that in engagements at range, either the entire fleet should get back, or the entire fleet should fail to get back. They are sailing as a unit, and the enemy fleet is not very close to them; if one ship has a path back, they all do. The code makes two exceptions; first, if some ships have Run Past orders and others have Engage orders, the ones with Run Past orders have better odds to get back, and I think it's fine if one does and the other doesn't, since they are clearly manuevering separately. However, in this case, if two ships have the same orders, they should get the same result. Second, if ships are of different qualities, the higher quality ship has a little better chance to get back. In rare cases this can cause ships with the same orders to split up. I can live with that rare chance.
It seems clear to me that in engagements with broken lines, it's every ship for itself, and there should be ship-by-ship rolls to get back to harbor, meaning in a big battle, some will (typically more than half but not always) and some won't.
What about an engagement in line ahead but at close quarters? Here the ships are sailing together but the enemy is very close. Ships in line ahead are typically spaced 50-100 yards apart, so a line of 10 or 12 of them is one-third of a mile to two-thirds of a mile long, and the engagement range will be 50 yards or less. Here it seems to me that a ship at the head of the line might have a clear path to get back to harbor and one at the rear of the line might not. So the code will also do ship-by-ship roles in battles at close quarters, line ahead. The one-roll-for-the-whole-fleet code is invoked only in battles at range.
I think this is the Right Thing but I invite discussion if someone thinks otherwise.
Steve