View/Verify XXX.terrain quantized mesh data

We are generating quantized mesh data - we can see the data is non-zero and appears to be valid (in fact, we are using ctb-tile to generate the tiles, so they SHOULD be good). However, in Cesium the wireframe is completely flat with no elevation. So something is wrong. We do save the terrain tiles (XXX.terrain) to a disk cache as files, so that we can verify them. So we are wondering if there is some way of viewing these files offline.

Thanks for any help!