Spark plug keeps turning. I cannot get it out.

Question: My generation free-spark plug? I cannot remove it. It just keeps turning.
A little bit of background, before changing the head gasket, I did a cylinder leak-down test. That had an adapter on it. It seems the adapter got stuck in the spark plug hole.
I look with my light. A camera light and seen, wow, the adapter came off.
Went to the store, got an easy out and a tap. Came right out, I ran the tap, just a turn or two, and the spark plug the whole was fine.
A few months later, I did a head gasket, and I had no problem with this cylinder.
Fast forward this weekend, the plug keeps turning and turning.
I got fatigued, and I said, You know what, I think this has been like this for a while. So I put the car back together with three new plugs start of the motor. I hear no compression leak. The car runs well.
Drove it 140 miles yesterday.
Use the car for work like a taxi cab. Any advice? I think the car is going to continue to run well.
The option is to take the head off??. having it retapped. Or getting an extra head, I'm doing a swap.
But if it runs good, I'll do that in the future before it gets cold two hundred and thirty-two thousand miles.

 

Makes perfect sense. Never really thought about it. The coil kinda locks it down some.
As far as a machine shop. You mean I can maybe find one who can get it out on the car.. kinda like a repair shop.??
When it fails think the plug will blow out.
How should I prepare. I have a feeling it may have been like this awhile.

 

There's a prius shop. Or a car or a guy that has a lot of prius's in the parking lot. I'll drive by and ask.

 

as you have been helping me all along with all the great info. I will try to find a machine shop and if they seem fair , I will remove the wiper covers and drop it off.
Recap. While doing a cly pressure test last year. The cheap attachment that adapts the gauge to different cars. Got stuck in by accident.
I brought a tap from the store..turned in in alittle . adapter came rt out. chased the first few cly head threads. was ok.
did the head gasket. replaced the spark plug again. no problems.
something went wrong somehow.
i burn less that 1 qt of oil every 5k..i would think about swapping the head can do in 5 hours . but. this head is good. so machine shop it is.