Naval units: 50+ attack bugs?

[Vulcain]

I've tweaked all units with an era multiplier, increasing strength of modern units. I've made extensive testing with the battleship. Something weird happened... Below 50 attack, the combat result corresponds to the attack vs defense ratio of the combatting units. But setting the battleship to 51 attack makes it no stronger than a galley... It's almost always destroyed.

I don't have the same problem with tanks or other ground units, which makes me think that 50 attack is a cap for naval units.

Any feedback?