I decided to give the plugs a clean and wouldn't you just know it! The first 3 came out and went back in no problem, nice and straight, finger tight all the way untill you need to crank that last turn to lock them in.. And then came number 4. Came out no problem , but upon trying to line it up to get it back in I could see some chewed threads. No matter how many times I've tried, it only goes in about 5 turns then seizes up... I don't want to force it in because that would mean a new cylinder head the next time I need to change a plug... Any ideas on how to resolve?