"Ghost Boats" Floating across land

As you can see it's hard to determine what is causing the issue, even if the fact that it's a visual bug seems to point out a discrepancy between what the server and the client "think" about the position of the boat. Unloading it also has some effects on the bug, but the inconstancy makes it hard to understand properly what is wrong. This is not the only way to encounter the bug, I just explained it in a controlled enviroment. I apologize for my English.

proof https://www.youtube.com/watch?v=B98yRTSspVc&feature=youtu.be