Preview Meshes in Material Instances lose their association to material on close.

When you assign a Preview Mesh to a Material Instance, save and close the instance, on reopening instance, the Preview Mesh will not retain connection to the Instance and will revert back to its assigned Material until a Instance value is changed, the Parent Material is reassigned, or the Preview Mesh is reassigned.

Also reproduced in 4.9 Preview 3 (Launcher) and Main-Promotable-CL-2649225

Before Closing and Reopening, Beachball assigned:
[Image Removed]

After Reopening Material Instance:
[Image Removed]

1. Open QAGame Editor
2. Open MaterialInstanceConstant'/Game/Maps/TestMaps/RenderTestMapAssets/ColoredMatte_INST0.ColoredMatte_INST0'
3. Assign StaticMesh'/Game/QA_Assets/Mesh/BeachBall.BeachBall' as the Preview Mesh
4. Save the Material Instance (make writeable if necessary)
5. Close Material Instance
6. Reopen Material Instance

RESULTS: The Beachball has reverted to it's original, assigned Material

EXPECTED: The Beachball mesh in the Material Instance should show the Material Instance applied to it.