@chris fullmer said: Thanks for posting this. I've submitted the model and the materials as a bug to be fixed. It is the dark wood material that is actually causing the problem. Do you know anything about that jpg or how it was created? Chris Yes, you are right. That dark wood texture pic was downloaded from Internet. Then I screetshot part of it to use as surface texture in my model.

Thanks TIG and Pilou for the clue. I would make the paper face then extrude cause it involve more than 10 different level on top face.

No trouble caused. Glad you got it worked out.