When an entity is loaded (Chunk reload, /Summon, ect.) it doesn't render the entity in the direction of the Rotation tag values, instead it will face north.

• Rotation tag still has correct values stored
• "/tp <selector> ~ ~ ~ ~ ~" gives entity the correct orientation from the Rotation tag

Example:
1. /summon Creeper ~ ~ ~

2. /tp @e[type=Creeper] ~ ~ ~ 180 ~
3. Leave world
4. Rejoin world