The bottom face seems to be mentioned twice (1, 2, 3, 4) & (1, 4, 3, 2) (which contradicts the informal proposition about unique faces). And “front” face is not found. 
Guess it should be
-#1 IfcIndexedPolygonalFace: ((1, 2, 3, 4)
+#1 IfcIndexedPolygonalFace: ((1, 2, 6, 5)
#2 IfcIndexedPolygonalFace: ((6, 2, 3, 7)
#3 IfcIndexedPolygonalFace: ((7, 3, 4, 8)
#4 IfcIndexedPolygonalFace: ((8, 4, 1, 5)
#5 IfcIndexedPolygonalFace: ((1, 4, 3, 2)
#6 IfcIndexedPolygonalFace: ((6, 7, 8, 5)
