The reason should be in FMaterialShader::GetParameterCollectionBuffer , Scene is nullptr and cached value GDefaultMaterialParameterCollectionInstances ** doesn't update.

Steps to Reproduce
  1. Create a MPC(material parameter collection) and add a vector parameter
  2. Create a UI Material, add MPC node and connect to emissive port
  3. Create a UMG, add a image widget, select the UI Material as image brush
  4. Add a UMG animation track, add some keys to the MPC vector section
  5. Drag time label in the sequence

result: the image brush doesn't change in UMG editor preview

[Image Removed]


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ComponentUE - Editor - UI Systems - UMG
Affects Versions5.3
Target Fix5.5
Fix Commit32412214
Main Commit32412278
CreatedJan 23, 2024
ResolvedMar 21, 2024
UpdatedMar 22, 2024