When an entity riding a horse, horse isn't rotating to the direction where rider want to go.

When an entity {skeleton, zombie...} riding a horse, horse isn't rotating where rider want to go. You can see this bug in the action if you run command for spawning a skeleton trap where you can see that horses aren't rotating and they are walking in random angles based on where skeleton want go.

Command for spawning skeleton trap: /summon minecraft:skeleton_horse ~ ~ ~ {SkeletonTrap:1}