I am not sure if this is the correct term but I call bottles with stains up the cork to the top, or wet and moldy tops, corked. I have noticed that i get more of these from local wineries than from store fronts. Is 1 out of 15 or so to much? My wineries replace without problems, but now and then i order from out of state.
Also what are the advantages of cork vs plastic other than tradition? Does cork add flavour?