Ans from HAN clan joined my side of a battle against 2 swedes. I originally thought this was to help me, but he had no intention of fighting the swedes and only joined to lock the BR, so my group members could not join my side of the battle and actually help. He originally pretends to 'help' but misses every shot, eventually he just puts his sails down and sits, providing zero assistance. He didn't shoot an enemy's hull even once, although they gave him clear shots. It is clear they knew he was working with them.
Jump to these times just to see the intentional misses. 5:19 6:21 7:37 9:38 (links in video description)
I would say this is as bad as sinking my boat in green on green, as I would not have lost the battle if he did not lock the BR. Also, I would have played the battle differently and run from the start, if I had known he would be of no help.