Instanced MovieSceneEventParameters does not save updated values upon level load

Any instanced Actor with a public MovieSceneEventParameter struct doesn't retain any altered values on level load.

Found in 4.22 CL#7053642

Reproduced in 4.21 CL#4753647 , 4.24 Main CL#7173985

Repro Steps:
1. Create a custom struct or use a premade struct from Engine Content.
2. Create a blueprint that is derived from Actor.
3. Create a public MovieSceneEventParameter in the Actor.
4. Place an instance of an Actor in a level.
5. Update the public MovieSceneEventParameter in the placed actor.
6. Save the level.
7. Reload the level.

Results: The instanced Actor does not retain the updated values for the MovieSceneEventParameter.

Expected: The instanced Actor retains the updated values for the MovieSceneEventParameter.