It's a skill of the ships, so nothing unusual. It does happen occasionally so just watch out, keep calm, tangle and curtain. And do fire your cannons until right before tangle turns off. The only real downside to that is that you gotta start all over again when they heal.
EDIT: checked piratia and apparently the chances of them using it is 5% when do get the chance to use it, in case you wanna know