Bees don't pollinates crops > 1 block below them

Steps to reproduce

1. Plant crops on farmland in an enclosed space with several blocks of headroom.
2. Place a beehive 4 blocks up the wall on one side.
3. On the other side, place 2 layers of dirt and plant flowers on it. The flowers should be at least 2 blocks higher than the crops.
4. Spawn 4 bees.

Expected results

Bees collect pollen, 3 bees enter the hive, and 1 bee waits outside the hive. The waiting bee drips pollen and fertilizes the crops.

Actual results

Bees collect pollen, 3 bees enter the hive, and 1 bee waits outside the hive. The waiting bee drips pollen, but does not fertilize the crops, unless it happens to swoop down to where it is just one block above the crops.

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Original description
Bees dont pollinates the crops