Foliage turns black! Need Help

I am having big issues with Foliage in UE4.19. Every time I save file and restart Unreal half of my foliage turns black. if you paint more trees/grasses they will turn back to normal, but after opening project will turn black again. It is not a light baking issue as if I turn trees back to green, they light bake as green. Is anyone, has any idea, how to fix this issue? I have the idea its caused by SpeedTreeColourVariation, but the issue is not a light baking and other Unreal older versions like 4.17 work well. Please help

Same issue here. It appears with 4.19 version (grass was ok with 4.18).
However, it seems to be only a viewport issue, grass goes back to normal when clicking play or when rendering a camera view in sequencer.