"Generate Lightmap UVs" breaks Shapekeys

[ludwigseibt]

Describe the bug 💬

When you enable "Generate Lightmap UVs" shapekeys brake and seemingly affect random vertices instead of the ones they are supposed to. Some sort of index mismatch I expect.
I am using Unity 6000.3.6f1 LTS

Steps to reproduce 🔢

• Create Object with Shapekey in Blender
• Export
• Generate Lightmap UVs
• Its broken

Files to reproduce the issue ♻

No response

Editor Version 🎲

Other (Provide details below)

Render Pipeline and version

URP 17.3.0

UnityGLTF Version

2.18.9

Operating System 👩‍💻

Linux

When does this problem happen?

• Editor Import
• Runtime Import
• Editor Export
• Runtime Export

Additional Info 📜

Unity 6000.3.6f1 LTS

Validations 🩹

• I have searched existing issues: no issue already exist that reports the same problem.
• I follow the Code of Conduct
• I provided a minimal reproducible example, including files when necessary.