Cannot remove spark plug from 2004 Chrysler Town Country 3.8l V6 - crossthreaded?

80,000 miles trying to change plugs. All is well except for one. The plugs itself broke loose and will come out halfway but then gets frozen solid. I can retighten, then loosen, retighten, then loosen almost effortlessly, but once I hit that midway point.. it will no longer budge. I bought this van used and I suspect that the plugs have never been changed before. The other plugs that I removed didnt look too bad but wanted to change them anyway. I suspect that it may have been crossthreaded. I tried running the van to make it hot then attempted to remove plug again. No luck. I am tried several times even with oil.. results are all the same. Any Advice?