swingcat,
If you have never tuned an extractor, be careful not to over-do it!
You said you have replaced it twice and still had the problem. I have a 40 cal 1911 and the extractor is caliber specific since it has to position the hook closer to the center of the gun. Did you get an aftermarket extractor or Colt? Did you specify a 9mm extractor?
Check for a broken hook on the previous extractor. If it's not broken it's probably still good and just needs tuned.
Also you said it could be shifted a few degrees at the "rear". If you call the rear the part held by the firing pin stop, then the firing pin stop may be too loose. You can get an aftermarket part that is slightly oversized and have it fitted for tighter assembly. If it's at the hook end then some play is expected there.
To tune it, you bend it, forward of the bulge in the middle, between the bulge and the hook. Bend it toward the center of the gun for more tension. Bend a very, very, little at a time. To gage proper tension, slip a dummy round up the breech face and under the installed extractor, with the slide removed from the frame. There should be a little resistance but it should slide into place without much pressure or any rough, scratchy feeling. Once in place, you should be able to roll the slide, turning it like a cigar, through 360 degrees without the dummy round falling out.
Mikey