Hiya. I can't really show it cause it's for the game project I'm helping on.... Under nda and that. I'm off to center parcs early in the morning but if I get a chance before I leave I'll pm you a shot.

3 possible reasons I am thinking of. One is that the process I have been using alot lately is to model my bases in Maya, sculpt in z, then export the sculpted level 1 to Maya for uv-ing and then importing the uvd mesh back to z. As the topology is always the same the detail transfers no problem onto the newly uv'd mesh.... But in the current case there were a couple of verts that somehow got adjusted so there are a couple of issues with how the detail transferred.

But also the model has some very thin areas.... You know how zbrush sometimes has
issues with very thin geometry, such as fingers, where if you sculpt on one side it pulls in the other side in the same direction....
Also.... The model has some parts which are just single sided geometry.... A few edges just extruded out from the model.... And I'm wondering if this could be causing an issue also.

I did try briefly polypainting over the ( seemingly total) mask, but nothing came out on the model.

I'll try post you a shot in the morning.