Falling blocks convert to blocks when falling on top of a boat

The bug

When a falling block falls on top of the surface of a boat that is perfectly aligned with the block grid, it converts to a real block and then back to a falling block. This repeats constantly, causing the falling block to flicker.

It is to be expected that the sand block does not convert to a real block since it doesn't land on a block.

To reproduce

1. Place a chest

2. Place a boat on top of that chest

3. Drop another boat on top of the previous boat

4. Drop a sand block on top of the boat
   → ❌ The sand block starts to flicker

Video