I would suggest looking at a speed build of this model and comparing the placement of pieces with that of your own.
So, let's try...this guy's video => The Austrian Lego Fan seems to have banged out a step by step build of this model, which shows a many angles of the area you're have issues with.
To get those butt-dragging results, you may have got your springs pinned in the wrong hole. Hey, but we can give more input if you provide a pic or two.
Both pictures are the same. One is text-less so the words don't get in the way.
Focus your attention on these spots. Is each spring pinned to the correct hole?