More than likely you still have some "meat" either in the ear canals or deep inside the naval cavity. Without beetles getting into the tiny crevices in the ear canal that junk will be nearly impossible to get out without breaking out the canal. It's super easy to do and you don't notice it on the final product. Just take a screw driver and insert it or hammer it into the canal, put some force down and most of that canal bone should break free fairly easily. Once you do it, you will easily see what bone will "break out" or come out easy. Almost like an entire separate bone section to the skull. It's amazing how much tissue gets left between that and the skull.