By default (since 4.5) a lightmap channel (UV Channel 1 in UE4) is created on import unless you uncheck the import option for “Generate Lightmap UV.” This is where the second UV you were finding was coming from.
By default (since 4.5) a lightmap channel (UV Channel 1 in UE4) is created on import unless you uncheck the import option for “Generate Lightmap UV.” This is where the second UV you were finding was coming from.