Geometry bug when importing OBJ files into Keyshot 5.0

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I am receiving a glitch when importing OBJ files from SketchUp 2016 into Keyshot 5.0 Pro on windows (Have also tried importing same obj files to a mac with Keyshot 7 wand receive the same problem). When creating a room without a roof, if i leave openings for doors the walls seem to create geometry to link some walls, creating a "roof" as you can see in the attached images . The same geometry also pops up when importing tables, if i make a curved top or wall the top or base will create a face over the curve. Also recieved the problem from objects directly imported to sketchup from the 3D warehouse.
Any help would be appreciated. Cheers