I have a wall mounted faucet that leaks around the stem. I have tried to remove the stem to repack it, but I cannot get it out. I thought that once I removed the compression nut, the stem would unscrew out, but it reaches a point where it will not turn any more. There is something white underneath the compression ring that feels like plastic. I'm afraid to dig it out because I may not be able to replace it. Any suggestions?