Invisible triangles in hkpExtendedMeshShape

Hi,

I'm developing a windows application with Havok 2011-2-0 (hk2011_2_0_r1). My platform is Windows7 Professional and VisualStudio 2010. I use hkpExtendedMeshShape for the dynamic rigid body, and I found a problem. The tiny triangles are invisible via visual debugger. Is there any restriction for hkpExtendedMeshShape?

I attach theimages of original triangle mesh  (Autodesk FBX), and hkpExtendedMeshShape via visual debugger (with invisible triangles). 

Thanks in advance.