Additive Animation does not work as intended when Ref Frame Index is more than zero

In some conditions, additive animation shows different/wrong behavior on Standalone Game and packaged game, from the other PIE. Watch the attached video.

[Link Removed]

The key points to reproduce this issue;

• Additive Animation refers key index > 0
• Save Additive Animation asset on UE5.2 and later.
• Run a Standalone Game, not selected viewport.

Whenever you save additive animation sequence on UE5.2 and later, the additive animation shows a behavior which is like Ref Key Index is zero, in a standalone game and packaged game.

From the customer's report, UAnimSequence::GetNumberOfSampledKeys returns incorrect number (probably zero). This could make actual Ref Key Index being zero by clamp. This does not happen in with-editor type play mode (like selected viewport) since GetNumberOfSampledKeys can return expected value by different code path. Also, the issue may depend on what version the animation sequence asset is saved by. That's why you do not see any issues on Third Person template. 

1. Create a new project with Third Person template.
2. Open MM_Land 
3. Press Ctrl+S to save
4. Launch a Standalone Game
5. Hit space to jump and see weird land animation.