Entities with Motion picked up by Minecart cause Minecart to stop

This relates to:

• MC-64836

• MC-71916

• MC-42637 (maybe)

It seems like mobs in Minecarts aren't able to control them (except chicken jockeys). This is different to boats and seems to cause some problems.

When a minecart picks up for example a entity which is moving (like a Zombie), it will some kind of take the Motion value causing it to stuck for example at powered rails next to a block.