The issue you're experiencing with strange lines appearing in Unity while your skeleton animation looks fine in Spine is likely related to mismatched export and import settings between Spine and Unity. Here are a few steps to troubleshoot and potentially resolve the issue:

1. Check Export Settings in Spine:

   • Ensure that your textures are exported with the correct alpha settings. If you are using Premultiplied Alpha (PMA), make sure that this setting is consistent throughout your workflow.

2. Check Import Settings in Unity:

   • Verify that the texture import settings in Unity match the export settings from Spine. For example, if you exported with PMA, ensure that Unity is set to handle PMA textures correctly.
   • Disable Generate Mip Maps in the texture import settings if you are using straight alpha workflow and ensure color bleed is applied to all transparent pixels.

3. Color Space Settings:

   • If you are using Linear color space in Unity, note that PMA textures are not supported. You may need to switch to Gamma color space or adjust your texture settings accordingly.

4. Multiple CanvasRenderers:

   • If you are using SkeletonGraphic, enable Multiple CanvasRenderers in the Advanced settings of the SkeletonGraphic component in the Inspector.

5. Update Spine and Unity Runtimes:

   • Ensure that you are using the latest versions of Spine, spine-unity, and spine-csharp runtimes. Outdated runtimes can sometimes cause visual artifacts.

Here are some useful links and references:

• Premultiplied vs Straight Alpha Import