FireFighterZero
Captain Zero!
Damnation Stephen. Tell the bastards you dont want a warranty on the next one.
trained mechanic who was and is in the biz sorta, I can say this is one industry that a person does not always get what they pay for. 

That was the 038 Av ,B .I think this is the one. Correct me if I'm mistaken please, Al.
https://www.masterblasterhome.com/showthread.php?10006-038-mild-port-job
We were just discussing the 5.4 at work today .Here's what they say .Fire it and let it warm up .Real quick like if you can back the plugs off about a quarter turn then fire it up once more .Once it's good and hot screw them out .I've never worked on one so I really don't know if that works or not .
have improved(more) threads but Ford sourced or was supplied a two piece plug. Carbon deposits glue the bottom part of the plug into the head and snapola when you remove them. Once the newer one piece style plugs are installed it should never be an issue again.