I have problem with brightness in my game.
Some entity brighter then other, BUT it not texture problem
Here is screens in editor all looks fine but not in game...
i edit texture in photoshop to make in more dark but it not helps.
FPE

btw its from free PirateMyke roads pack

My roads looks fine now, lol i just restart GG if i just open level without restart gg its not add new texture.

Those were not made for those shaders.
Have you tried the entity_basic shader in the FPE file?
With the material I defined in the FPE file of 3 GG will use the common gloss and metalness ones in the effectbank/reloaded/media/materials folder.

But it looks ok with the defaults after your reboot.

Useful info:
Metalness - black is dialectric, White is metal

Gloss - Black is shiney, white is rough

Specular - Mostly grey scale except for metalic objects, then the reflectence color of the metal is used for the specular color. Not used in PBR

Roughness - Black is Rough, White is shiny - Game Guru does not use at all.

Displacement - White is height, black is lows - not fully implemented yet.

Normal direction +X -Y +Z