When "Support Material Layers" is Enabled Material Instance Parameter Values Reset to Default Value When Override is Unchecked

If "Support Material Layers" is enabled, every time you uncheck an overridden parameter box in a material instance the value of that parameter will reset to its parent's default value instead of staying the same.

Found in 4.19 CL# 4033788, 4.20 Preview 5 CL# 4173640, 4.21 CL# 4207835

1. Open the editor
2. Enable "Support Material Layers"
3. Restart the editor
4. Create a material with a parameter
5. Create a instance of the material
6. Check the override and change the parameter value
7. Uncheck the override

Results:
The value of the parameter is reset to the parent materials default

Expected:
The value should stay the same as it does without "Support Material Layers" enabled