The bug

Since 20w09a, when ejecting an entity from a Minecart into an opened trap door by using an activator rail, the game will consider this place to be unsafe and place the entity somewhere else even though the block below it is safe.

It would be expected that when the Minecart drops the entity, it would verify that the block below the open trap door is safe to proceed.

Video

https://youtu.be/vB7-0sPqhts