I’m not sure what you mean by animation playing weirdly ingame…
If you’re talking about some keyframes not acting stop motion, the second video has the same thing.
It’s a little hard to see, but at the ending of the animation it glitches out in game.
Also, the sine keyframes are on purpose. I’ve just had the same stop motion thing happen last time I tried to animate in stop motion and play it in game.
I made some adjustments to the animation and it’s a lot easier to see now.
I found a solution. When using fill in Moon Animator, then setting it to none, it fixes the issue. I am posting this to assist anybody else who has the problem. Have a nice day!