Everytime I´ve used Unreal I have seen this issue. Since the PBR workflow appeared the artists are always checking the Unlit Viewing Mode and many times I´ve heard “This is not my texture!”. I always suggest to check the Base Color Buffer Visualization and that way we can see the texture exactly as in Photoshop or SubstancePainter.
The metalness is affecting the way we see the colors on the Unlit Mode. Any reason? Are we missing something?