Chester and all of his contents are duplicated upon moving between worlds using the Seaworthy. It appears to happen if chester was in the caves, then upon returning to the surface drop the eyebone in a backpack and use the seaworthy. Upon returning to RoG, the duplicated chester will follow the eyebone, but after picking up the eyebone and re-entering caves, all duplicate (not including the "original") chesters will follow the player even if the eyebone is dropped. If a duplicate chester is attacked, it will cease following the player, and instead roam around randomly on its own until killed. If there are duplicate chesters following the player (without having the eyebone) when the player uses the Seaworthy, all of them will be duplicated in the world being traveled to and they will immediately start roaming around at random (there will be a group of random roaming ones, and a group that continues to follow the player, apparently of equal size). This makes it possible to duplicate a practically infinite number of chesters at once. If duplicate chesters are killed, it seems they do not respawn. I've not tested it, but I assume it also works with Shadow/Snow chester. The attached video was taken on a 1st gen ps4. The RoG save was created a couple weeks before this report and merged with the SW world before world hopping in RoG if that matters.
Steps to Reproduce
1. Bring chester into a cave (possibly filled with tasty loot) 2. leave cave 3. drop eyebone (may be necessary to have it in a backpack, not sure) 4. use Seaworthy 5. profit
This issue has not been confirmed by a developer yet.