Chester and Glommer in Shipwrecked

I used the seaworthy to go from Shipwrecked to RoG. I picked up my eyebone and went to the cave to get lightbulbs. About a day later, I come back and spend about half a day above ground in my RoG base. I drop the eyebone (which has glommer's flower) and use the seaworthy. I enter Shipwrecked and I see chester hopping around. I follow him to my fish bone (It's at the same island as the seaworthy). Now chester follows the fish bone, and glommer follows chester, and packim bagins also follows the fish bone. 

I haven't tried going to the water or going back to Rog yet. 

PS: The youtuber Volx has a video about it.

EDIT:

I went into my boat, chester didn't follow me. I went to RoG, my old chester and glommer were still there. I went back, and the duplicates were still there and functioning as they did before.

After I came back from the caves, I put a beefalo hat in RoG chester, the shipwrecked chester doesn't have the hat. So the bug is related to the caves in some way.