I have just bought the Hartford XL second hand from a mate. I have exactly the same problem! I am experienced erector?? and this one had me stumped.
I thought it was wrong poles in wrong slots or pegged out incorrectly. Put it up and down 3 times now. Relieved to see its not just me but really annoyed its clearly a problem with the tent which is otherwise superb! As soon as my kids get in this I can see its going to get ripped in the corners. The tension problem is in exactly the same place for me. And also 2 snapped poles as well! Not sure what to do...