How did my headset get this way? I have a newish bike I bought second hand.  To the best of my knowledge, the headset has not been dismantled as it all looks original.  It's a threaded headset and a 1" fork steerer tube.  It looks awfully like this Ritchey headset apart from the Ritchey logos - but I'm pretty sure it came out of the same factory. https://www.chainreactioncycles.com/ritchey-logic-threaded-headset/rp-prod39820 

It has never quite sat right - and pressing on the handlebars always made a slight squeaky sound.  I thought I'd have a go at dismantling it using the right 32mm wrench on the race.  The locknut came out no problem - I used the wrench to loosen it and then it came out just with my hand, so I know the steerer thread was fine.  But then I tried to take the race out, and man it was hard, I had to use the wrench with full force.  I managed to get it about 1/8" from the top before I stripped the nut on it.  And at that point, it looks like it's been cross threaded as the race doesn't quite sit parallel to the tube end.

So the question is how could this have arisen?  Is it possible the factory assembled a cross threaded race and just forced it all the way down to a point where it sorta passed quality control?  Or is something more sinister at play here and do I have an even bigger problem?  And as for any tips on how to get the race out?  I'm thinking of sawing through the nut itself but not sure if this will work.  Any ideas very welcome.

Thanks in advance.
Nathan's comment is solid -
Assuming Stephan removed the keyed washer when he took off the lock nut...

How did it get this way?
It's hard to say, here are some possibilities.  


It may have been cross threaded from the factory. Seems like a long way to cross thread something - all the way from the top of the steerer tube to it's current   location and then back up to almost the top. Cross threading usually results in some thread damage that should be visible in the steerer tube threads.  
A previous owner may have cross threaded it. Same observations as option 1.  
I can't think of anything besides cross threading (and Nathan's suggestion)  


How to fix it?
First, check Nathan's thought - look for a keyed washer sitting on top of the race nut. It's labeled "Washer" in the diagram below.  




Assuming cross thread - since you are 1/8 of an inch from the top with a rounded nut I'd look for a tool that will like a large vice grip to clamp on to turn in the last little bit. Some penetrating lubrication might help.
I'm worried about cutting the race off. It's hard to imagine how you can cut it without damaging the steerer tube threads. If you use some kind of a small cut off saw, don't go all the way through, make a couple cuts and experiment with a chisel to remove a section of the race it might not damage the threads.
I've read of people having success using heat to remove stuck nuts. I've never had any luck with it.


Maybe someone else will have a better suggestion.

If the threads on the steerer tube are OK all you'll need is a new adjustable race.
If not, you may be able to clean up the threads with the right threading die.
If not, you'll need a new fork