Steps to reproduce

1. Make a nether portal in the nether.
2. Place a boat in it.
3. Go though the portal.
4. TP to 0 0 0. If there is a lava lake at this position, fill the area around it with stone and make a hollow air chamber at 0 0 0, then repeat these steps.
5. Relog.

Expected result

You find the boat in the OW portal in step (3)

Observed result

Sometimes you find the boat at 0 0 0 in step (4) or (5). This seems to depend on the location of the destination portal because it happens for some portals and not others when I test. The boat may be invisible until you relog.

Note: this also occurs sending boats from OW --> Nether, but in that case the the boat falls into the void because there is no block below 0 0 0 to support it.