Is it possible to have multiple social things revealed at once? For example, can you find a Royal Convoy, and while its still showing on your map, find a social chest as well?

I ask because I found a Royal Convoy a few days ago but its icon never disappeared. Any time I go to its location, it's just a blue royal convoy icon floating on top of the water. I only need 2 more social chests for the challenges related to them but I've been running around Havana, Kingston, and Nassau for several days now and haven't found a single chest. I'm wondering if it's because the game thinks there's still a royal convoy out there.

Also, since that was my 3rd royal convoy that I had taken down, but glitched and remained on there, I got the challenge for taking out 3 of them but I didn't receive the Aquila's Figurehead (plunder 3 royal convoys).

Any ideas?

On a slightly unrelated note, my harpoon 6 different sea animals is also glitched at 5/6 even though I have harpooned the 3 different sharks and whales multiple times and have at least one of their bones/skins still in my inventory to show for it.