The bug
If you give a score value to an entity, then quit the world, and open the world again, the entity will lose the score.
If you give a score value to an entity, then quit the world, and open the world again, the entity will lose the score.
(Unassigned)
Confirmed
Minecraft 1.8.7, Minecraft 15w43a, Minecraft 1.11, Minecraft 1.13.2-pre2
Retrieved
Confirmed for all rideable entities.