UE 5.8.1 unreliable for skeletal animation production

General Issues and Bug Reporting (Unreal Engine)
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Summary

UE 5.8.1 – Sequencer Animation Bake Causes Severe Skeletal Stretching / Incorrect Bone Transforms and Skinning Issues

I am experiencing multiple serious skeletal animation and skinning issues in Unreal Engine 5.8.1 that not happened ever other unreal engine versions.

The most critical issue happens when editing animations in Sequencer with an additive Control Rig.

Inside Sequencer, the animation looks completely correct. Bone positions, hips movement, shoulders, hands, and the overall character pose all evaluate normally.

However, once I bake the Sequencer result to an Animation Sequence, the resulting animation can become severely corrupted.

Main issue

For example:

  • The original animation is added to Sequencer.
  • An additive Control Rig is used to make pose corrections.
  • The result looks completely correct inside Sequencer.
  • Changing the hips translation from around 15 to 0 looks correct in Sequencer.
  • After baking the animation, the character’s arms can suddenly stretch.
  • Hand positions may be different from what is shown in Sequencer.
  • Shoulder corrections may not be preserved correctly.
  • Some major/extreme pose changes are successfully baked, while other bone adjustments are missing or evaluated incorrectly.

This is not just a visual difference in Sequencer. The generated Animation Sequence itself produces an incorrect result.

I tested both the normal Bake Animation Sequence workflow and the newer Auto Bake workflow. Both can produce the same stretching/corrupted skeletal result.

Additional skinning issue in UE 5.8.1

I am also seeing incorrect skinning/deformation on older skeletal assets that worked correctly in previous Unreal Engine versions.

Some clothing meshes that deform correctly in UE 5.7 produce incorrect skinning/deformation in UE 5.8.1.

In some cases, exporting the affected skeletal mesh and re-importing it through Blender appears to fix the skinning problem, which makes it look like UE 5.8.1 may be evaluating or converting existing skeletal/skinning data differently.

Tests performed

I have already tested several possible causes:

  • Fresh/verified Unreal Engine 5.8.1 installation
  • New Level Sequences
  • New additive FK Control Rig tracks
  • Manual Animation Sequence baking
  • Auto Bake
  • Skin Cache-related settings changed/disabled
  • Unlimited Bone Influences disabled
  • Experimental Skeletal Mesh Chunking disabled

None of these fixed the animation baking/stretching problem.

An important detail is that the same project does not show these problems in UE 5.7.

What Type of Bug are you experiencing?

Animation

Steps to Reproduce

  1. Open an Unreal Engine 5.8.1 project containing a skeletal mesh and an existing Animation Sequence.

  2. Create a new Level Sequence and add the skeletal mesh/character to Sequencer.

  3. Add an existing Animation Sequence to the character’s Animation Track.

  4. Add an Additive Control Rig on top of the animation.

  5. Make several bone adjustments with the Control Rig. For example:

    • Change the hips/pelvis translation.
    • Adjust the shoulder or clavicle rotation.
    • Adjust the hand position.
    • Add a more noticeable pose correction to another bone.

  6. Scrub and play the sequence and verify that the character and all Control Rig modifications look correct inside Sequencer.

  7. Bake the final result to a new Animation Sequence using Bake Animation Sequence.

  8. Open and play the newly created Animation Sequence outside Sequencer.

  9. Compare the baked Animation Sequence with the pose shown in Sequencer.

Result

The baked Animation Sequence may not match the correctly evaluated pose shown in Sequencer. Depending on the animation, one or more of the following can occur:

  • Arms or other parts of the skeleton become stretched.
  • Hand positions change.
  • Hips/pelvis translation corrections are missing or incorrect.
  • Shoulder/clavicle corrections are missing or incorrect.
  • Some Control Rig changes are preserved while others are not.
  • The skeletal deformation can become visibly corrupted.

The same issue can also be reproduced using Auto Bake instead of the normal Bake Animation Sequence workflow.

The same animation workflow and assets work correctly in Unreal Engine 5.7.

Expected Result

Expected result

The Animation Sequence produced by baking should match the final evaluated pose shown in Sequencer.

If the character looks correct in Sequencer, baking that animation should not introduce:

bone stretching,
incorrect scale,
incorrect hand offsets,
missing hips translations,
missing shoulder adjustments,
or different skeletal deformation.

Observed Result

Actual result

Sequencer evaluates the animation correctly, but the baked Animation Sequence can contain/evaluate significantly different skeletal transforms, including severe limb stretching.

Older skinned assets can also deform differently in UE 5.8.1 despite working correctly in UE 5.7.

This currently makes UE 5.8.1 unreliable for our skeletal animation production workflow because there is no guarantee that the animation visible in Sequencer will match the resulting baked Animation Sequence.

Affects Versions

5.8

Platform(s)

Windows

2

Thanks for all this, it explains a lot.

Personally, I gave up animation in Unreal Engine since version 5.7; I do everything with external software.

1 Like
3

Encountered a similar issue and was testing for hours, not sure if this is the same issue. What worked for me was ticking the “Set Retarget Source Asset” This is one of the options after you pick a name and folder for the bake. If you already have the animation sequence baked, you can also open it and set the Retarget Source Asset to your metahumans body mesh.

1 Like
4

I really like being able to make quick animation adjustments directly in Unreal when something does not look correct or does not fit the scene. Editing animations in Sequencer can save a significant amount of time during iteration.

The Sequencer editing workflow itself is very useful, but the current baking issues make it unreliable for production.

5

MarcggAN identified the actual cause of this issue.

In UE 5.8.1, the source Animation Sequence can have the correct Retarget Source Asset assigned, but when a new Animation Sequence is created through Sequencer baking, that retarget source is not propagated to the baked asset.

As a result, the baked sequence falls back to the Skeleton’s default retarget/reference data instead of using the intended MetaHuman body mesh. This causes incorrect bone translation evaluation and produces the extreme stretching/deformation seen after baking.

Enabling Set Retarget Source Asset in the bake options and assigning the correct MetaHuman body mesh fixes the resulting animation.

So the underlying problem appears to be that UE 5.8/5.8.1 does not preserve or automatically assign the source animation’s Retarget Source Asset during the bake process. This was not required manually in the same workflow in 5.7 and earlier.

Thank you MarcggAN.