serpentine 5
Started with your model post , changed to SU7, quick check showed 78 broken lines , 39 stray lines. Flatten it to remove any question about planer. If you select various faces in the model you will see areas where they are selected and they should not based on wall etc. Some are caused by coplanar lines , duplicate faces etc. Where these errors came from? Probably as TIG stated but they can also be caused by you as you make the model. Make sure you spend some time on the video tuts so you under stand inferenceing use. Once you get to this model level it can get difficult to correct so slow down and hurry up is the best approach. There are plugins that can help you trouble shoot but best to under stand the SU basic capability first.
S
