Hmmm not sure, I tested and didn't got the error, maybe check your importing settings?
Oh I see, how the models look like on Unreal? If I'm not mistaken smoothing groups affect how the model reacts with light, I think it should work fine.
I kind of got it to work, but now the model has the tall gray textures around them how could I move it?
Can I see how it looks like?
From what I can tell you're using tree01.png as a texture for bush01, bush01 uses bush01.png
dang what a crazy mistake, I could've sworn I was using the right material thanks a lot for the help