Spark plug loosens but then gets tighter

hi all, I'm replacing my spark plugs and I got plugs 1, 2 and 3 out just fine but plug 4 (closest to the distributor) comes lose but as I continue to loosen it it begins to feel like it's tightening again. I'm nervous to keep going at it. Worth noting is the car was still fairly warm, I started the process after the car sat for 20 minutes after a drive.

Any ideas/suggestions? I pray the threads are not crossed.

Thanks!
-Mike

Yup those threads are fuct.

Get #4 as tight as you can before it "goes loose", leave it and hope it doesnt leak. You'll probably never be able to change that spark plug again.To fix it you have to remove the head and take it to a machine shop, or replace the head.

If you haven't already figured it out you should be using a torque wrench to prevent this.