Can't import more than 4 UV channels

In maya my mesh has 5 UV sets, everything was working fine until I started setting material for the part with 5th UV channel. I tried to create 6th set like LightMap, even if I have Skeletal Mesh Character, however nothing works…

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Hi! If I remember correctly every additional UV channel causes more draw calls. So too many UV channels is not a good practice in the sense of runtime rendering…