This is really strange 'cause I have experienced that "being stock in the a weird view screen" thing but not that specific situation.
*Please provide a savegame before attacking the Serena and .log files right after the problem occur.
Try these.
The saved game is at Kralendijk port after I've arrived, sold some cargo, sold some ships and been to see the governor.
Several other quests are also going on, though these never got in the way of the
Sirena (or each other) in earlier versions of PoTC.
Assassin: have recently been to Nevis to eliminate a smuggler
Strange happenings: have recently been to Bridgetown to receive wisdom from the Great Teacher
Lucas da Saldhana: is following me around like a lost puppy and probably wondering why I'm heading the exact opposite direction of San Juan
Pirate hunting: there's a 6th rate frigate somewhere near Bonaire
That last one did get in the way of the
Sirena, sort of, once. I put to sea from Kralendijk and the frigate was in front of me, some way out - to be more precise it was right in front of the fort, which started trying to do my job for me. I caught up with the frigate and boarded it, and while I was on the way I got a message that
Sirena had surrendered. Proceeding round Bonaire I completely failed to find
Sirena and "Sail To" didn't find it either. After reloading that saved game and putting to sea again, this time the frigate was not immediately visible. When I got to the other side of Bonaire I found both the frigate and
Sirena, boarded the frigate without any trouble, then sank
Sirena.
I can't remember whether the attempt to board
Sirena followed by the usual mess-up and reload happened before or after the frigate battle in which
Sirena surrendered and disappeared.
If the log files show previous problems as well as the most recent then you may also find something about a CTD which happened when I was on my way to Bonaire - I'd found a French group, attacked it, and was part way through boarding a ship when the game crashed. I reloaded my previous saved game (at Sao Jorge), went again to Bonaire, found a different French group, attacked it, boarded various ships and took them to Bonaire to sell.