in such a case, the first thing i always do. find out exactly the steps you use to get the mesh to the client and then what steps they take to open/load/preview it. i assume its some fbx stuff? i guess you do not have some weighted normals modifier or something going on on your end?
@Neox I sent them the original 3Ds Max file and the fbx file... I did use weighted normal but I collapsed the modifier stack, importing the FBX to blender or max and opening the max on my pc and different one and still no sign of the problems faced there. I am not sure what steps they take and I have tried asking them,…