is there a mod for fixing the bouncing ships

[karamazovnew]

Not all ships can capsize. They'd need to be either of big L/W ratio or very top heavy to do so. This usually means big Warships. You might even say that a flooded lower compartment can stabilize a ship. Capsizing should however be prevalent in rough seas with a compartment partly flooded (and empty of cargo).

Edit: However: a bank angle of more than 30-35 degrees usually means that a capsize (>90 degrees) is about to happen. This might not sink the ship immediately, it can take up to hours for an overturned ship to sink. I've seen many ships in SH that go beyond that angle without rolling over, which is completely unrealistic. In my opinion, ships should only bank if they have longitudinally divided cargo holds. Otherwise, the water would fill the compartment evenly. And, as stated before, a partly flooded comparment (any compartment that has air space above the waterline) should be very sensitive to banks, including the ones from a simple turn.

To give a good example, consider the Titanic. It had a massive rupture in the starboard side, which flooded many compartments. The ship didn't bank at all, it just sank bow first, in calm waters and stopped engines.