SPARK PLUG CROSS THREAD

If you are actually getting in 1/4 of the way (~10 turns or so), it is probably not cross-threaded and just has some debris or a bur in there.

Rethreading with a tap is going to cut new threads and remove metal.

Running a Thread Chaser instead, will clean up the treads by pushing the existing thread metal back into the correct shape.

I would try CHASING it before Re-THREADING it.

Put some heavy Grease, not Oil, in the chaser slots to catch any shavings that may happen.

But to do it properly you will need to pull the head to make sure you keep It all clean.

Removing Both plugs and blowing compressed air in the good hole will blow the nasty stuff OUT of instead of IN to the cylinder.

It is still a risky business no matter what you do.

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When replacing the plugs, or any bolt for that matter, while pushing it forward, start by turning it backwards using fingers only.

You will feel the threads "Jump" into alignment as they come into sync.

This trick is particularly important when replacing self-threading screws in soft materials like plastics where cutting new threads is a bad idea.

Thanks for the input. Any tips on pulling the head?

Try Bills solution first. You might be opening a can of worms, plus you will need an intake alignment plate tool and maybe new o-rings for the pushrod tubes/cylinder.

Let us know how it works out. 

I think it only takes about three turns to get my spark plugs a quarter of the way in, but if you are cross threading you should know it before you get much past ONE turn.  

Definitely try just cleaning up all the threads first.  Shine a bright light on them to help identify, if possible, the problem area.

Just curious, are these new plugs?  What engine is it, and what plugs are you using?

Old style plugs in a 912uls. I ordered a NAPA 12mm spark plug thread repair chaser.  I'll post results.  https://www.napaonline.com/en/p/SER3689