I am going for the 100% sync of all story missions and I am unable to get the 100% sync on this mission, the game is not registering one of the optional objectives. The objective that I believe to be glitched is "Damage the Royal African Pearl with an upgraded ram." I have a fully upgraded Jackdaw so I know that I have the best ram available, I have also destroyed all of the legendary ships to unlock the ability to do a "super ram".
I have the same problem as you. Also have all upgrades and beat all the legendary ships. Tried it a dozen times but I've been unable to get the objective done.
Did you find anything useful since you discovered the glitch?
I have continued with a 78% save (was 99% dammit) and was able to do it 100% now. My ship now wasn't fully upgraded yet and I didn't get the ram boost for defeatin all legendary ships yet. @ Allum, did you defeat all legendary ships? I think that might be what's causing it.
I as well am having this issue, and after trying multiple times, have had no more success than I did the first time. I tried to bring it up on the report page, but it will not allow me to send in any of my questions. I don"t have another save to load, and I certainly don't want to restart my progress from the beginning. Hopefully there will be an update for this soon, or I may be forced to completely restart,
Having the same problem. Stuck at 99%. I can't submit a bug report, and I can't submit a thread in the bug forums due to a weird glitch, so I figured I'd just bump this thread. Was kind of hoping for it to be fixed in today's Xbox One patch.