Incorrect foliage color in editor preview when using PerInstanceRandom node

When using PerInstanceRandom in the foliage material, the foliage in the editor preview has incorrect "broken" color. In the game preview, color shows up correctly.

Reproduced in 4.19.0 CL 3944462 and 4.20 Main
Unable to reproduce in 4.18.3 CL 3832480. This is a regression.

1. Create new, blank project
2. Create new material
3. Add "Add" node, connect to Base color and/or emissive color
4. Create a Constant3Vector node, set any color to it and connect it to A of the Add node.
5. Connect PerInstanceRandom node to B of Add node
6. Save changes in material
7. Create/import new static mesh and add new material to the material slot in Details panel
8. Add static mesh to foliage brush
9. Paint foliage into level
10. Save level and reopen

Result: Foliage material will show up as black rather than the set material
Expected: Each instance of foliage mesh will have random hue of color set in material