Boat completely desyncs client and server side

Example case 1: Underwater boats

1. Place boats underwater;
2. They stay in place, they don't float to the surface like they used to;
3. If you try to enter the boat, it seems to not work at first. However, it still functions like a normal boat would. Although you can still move around, the boat is your real position. Watch the attached video.

Example case 2: Lead

1. Place a boat anywhere;
2. Use a lead on it and try to move it;
3. It stays in the same place. The lead never breaks even though the player seems to be far from the boat.

Notes: Relogging causes all boats to appear in the correct location.