Material brightens after being painted as foliage

Hey there,
From yesterday on, as soon as I paint foliage, the material instance in use will be brightened, irreversibly. I spent the weekend trying to figure it out, no luck. Also, some of my foliage disappeared on startup, but this ship has sailed I already kissed it goodbye. It’s related though.
Tried switching mat, recreating mat, simplifying it to the core minimum, recreating the foliage type, updating to UE 4.20, now I’m considering uninstall and reinstall, looks like my foliage editor is just broken. Any thoughts ? Going crazy here. The difference might seems subtle to some, but for me it changes everything.

Image on the left of the 1st slide shows the mat instance preview, image on the right shows the mesh preview (using that same MI)