This one happens at odd times when doing multi people deck fights either joining or been joined. What happens is multiple things.

1. The combat sometimes just starts regardless of timer and not having clicked on the combat done button. It happens anywhere from 5 to 15 seconds from the start of a new combat round while deciding my actions.
2. Actual combat gets hyper speed, all sudden everyone moving way faster and some combat animations are just gone (meaning no movement, they just stand there but the damage/no damage still happens).

3. After fight is won, my or other player pirates are unable to move/interact with loot chests. The movement part goes from unable to cross the gangplanks to unable to move from their spot at all. And if they are unable to move at all then they can't seem to be able to open loot chests even if they spawn right on top of them. This does not exculds them from gaining gold/loot from the chests that were open by others.
4. This one just prior to joining a ship in battle. Sometimes if your ship is at an odd angle to the ship in combat and when you click X to join. You sometimes hang, meaning you not in the fight but at same time no longer targetable by other ships in the area either. But while in this state your unable to attack other ships but you can still sail to the point you can reach a port and dock. The time your in this odd state is generally linked to length of the ship battle you tried to join but didn't, though some times you get slingshot into the battle.