Existing animations made with curve editor breaking

I have made some animations that range from being around 2 weeks to 2+ years old. They have worked perfectly until 06.02.2025. I noticed that the animations breaking were made using the curve editor.

The animations work fine in the animation editor, but as soon as they are played in the experience or in studio, they glitch out.

https://drive.google.com/drive/folders/1RVVvNOZoADa-tTYxYr7RosawsUHdTwra?usp=sharing

Expected behavior

The animation should play as it does in the animator, like it did previously.

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Hi, thanks for the report, we’re looking into this urgently. Will let you know once we have an update.

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Hi there, thank you for sharing the video examples with us. Looking at the provided examples of in-game vs. in the editor, we’re not able to spot a difference or see the animation glitching effect that you’re mentioning. Could you please clarify the breakage that you’re experiencing or provide a test placefile that we can use to debug?

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Hi, thanks for looking into it.

I think it has to do with additional Motor6Ds, which I use here for the weapon. Here’s a placefile with a rig and the weapon. It’s a different animation, because I replaced the one in the video, but it’s basically the same result.

animation_bug.rbxl (81.9 KB)

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I’m having this issue too. It’s actually occurring with animations I’ve recently made using the curve editor too, the interpolation in-game just to seems to go absolutely bonkers causing body part and joints to randomly and suddenly twitch out in a random directions.

Below is a video showcasing these new bugs that previously didn’t happen with these animations.

This bug currently plagues all of the reload animations I’ve made for this game using the curve editor.

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We’ve rolled back a recent change that likely causes the glitches you’re seeing. You should no longer see the glitch after the change is fully rolled out (within the day).

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@HuntDownTheXboxMan Could you please provide the reload animation (either the animation Id or a placefile with the animation loaded) to help us further debug? Thank you.

Thanks for your feedback!
To my naked eye, these visuals look very similar (other than sword and swoosh replacing hammer).
Can you provide some guidelines on where to focus our eyes?
Thanks!

Thank you, it works again! Should I close this bug, or is it only a temporary fix?

Thanks for your feedback!
It’s great we’ve confirmed what broke your animation.
It’s a temporary fix in the sense that we had to deactivate an optimization that dramatically speeds up curve animations.
We would love to have a little more data to understand what’s actually going wrong visually so that we can fix our optimization.
Thanks!

Sorry for the late response, I was away from home for a while but I’ve set up a place file so you can easily test out the curve animations that I’ve found to be bugged. You should be able to just play test and equipping any of the tools will automatically play the locally loaded animations from the AnimationClips inside the rigs.

You can adjust the animation speed in the “ToolHandler” module which can be found through here: ReplicatedStorage > Modules > ToolHandler

Place file:
CurveAnimationDebug.rbxl (101.1 KB)

I’ve also discovered another bug with auto-tangent interpolation in-game that it will attempt to interpolate keyframes with identical cframes. I’m not sure whether this is intentional or not because of the animation editor interpolation not being identical to its in-game counterpart, auto-tangent is just spooky.

Anyways, I hope this helps!

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I added a few more animations that were broken to the roblox place file, before you reverted the optimization changes. The heavy sword swings were especially bugged. I don’t know if you can do anything with it now.

animation_bug.rbxl (94.8 KB)

The animations I used all had a handle in it, so I can just assume that the normal roblox rig is fine, but Motor6Ds have a problem with curve animations. I don’t know how it works on custom rigs though.

The moment where I noticed it happen was at around 8PM (CET) 06.02.2025 (US format). It happened in the experience first, and was still okay in studio at the time. Studio caught the bug too after 5 to 30 minutes.

That’s all I know about it.

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I’ve been facing a similar issue, starting today (2025-06-07); normal animations work fine, but my curve editor animation does not. I made a post about it before finding this one.

Thank you all for providing your placefiles to help us root cause the issue.

@SikeCSGO we have reverted the change that broke curve animations in-game. Have you had a chance to update or restart your Roblox Studio to pick up the revert? Please let us know if you still see the issue restarting or updating Studio.

Hi there!

We could reproduce the issue with the interpolation between identical cFrames and will work on a fix.

Thanks!

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Will the fix affect existing animations, or will they still act the same?

Your animation assets won’t be modified, but the way they play in-game will match what they look in the AnimationClipEditor.

Cheers!

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Hey, sorry for the late reply. I updated Studio today (2025-06-15) and the animation is still broken. I tried to overwrite my old animation, as well as publishing it as a new animation, but neither approach worked.

Edit: 2 days later, and I managed to “fix” it by changing the affected keyframe interpolation from cubic to linear. So not really a fix, just a workaround. I still think this post has been incorrectly marked as “fixed”.