i find not ALWAYS.. but most of the time, when viewing in 2d flat mode (not textured) the engine will auto locate LOTS of malformed faces/texture perpendiculars by discoloring them apart from the block..
say.. in 2d flat mode the block appears red, but one of the faces is discoloured perfect black (0,0,0) the same as the background of unused space on that very same shape
helps me, because i'm always getting into trouble carving around
so.. if your still having problems finding it, you might give it a once over in 2d flat mode.. could help