The boat floating in the air and getting random damages on the edges of the boat

(I can't have a screenshot)
Steps to Reproduce (Floating in the air):
1. Pillar up 21 blocks, then place a boat, sit in it and drive the boat to the ground (boat MLG)
2. Break all that 21 blocks
Expected Result:
When I get out of the boat, it'll appear on the ground
Observed Result:
When I get out of the boat, it doesn't appear on the ground, it instead appears on top of the previous pillar of blocks (which has been destroyed, so-called it floats in the air)
Step to Reproduce (Getting random damage (maybe falling damage) on the edges of the boat):
1. Get on top of the pillar of blocks
2. Stand on the edges of the boat that has "teleported" on this pillar previously.
Expected Result:
When standing on the edges, I just stand in the air with the boat
Observed Result:
I receive random damage (maybe falling damage) continuously if keep standing on the edges