Just got a chest from chapter 2 of a voyage and upon digging it up at The Crooked Masts, the chest was labelled "Pickup NO_NAME". It looks like a Captain's chest (red and gold) but I cannot pick it up unfortunately.
I know this is old, but I had just experienced the same problem. I was able to find a fix. I just ended up killing myself, re-spawning on the ship and going back to the chest location, where I was then able to pick it up! ruined immersion a little, but worth it to be able to finish the voyage.
