Creating a multi animation sequence that uses an additive animation does not play back correctly

Creating a multi animation sequence that uses an additive animation does not play back correctly.

In the attached project you can Play MatineActor and MatineActorLevelSequence(Converted matinee to level sequence) see that both plays back animations properly. However when trying to set this up by hand using what looks like the same settings I run issues where only the ThirdPersonWalk animation plays.

1. Open attached project
2. Open AnimSlots level sequence
3. Play the sequence

Result: The TestAdditive animation does not blend with the ThirdPersonWalk animation