Brass marks don't necessarily mean the extractor has a problem. In any case, you can remove them without risk to the finish by applying any copper removing bore cleaner with a swab until they disappear.
If you look at a picture of a Goldcup or other match tuned gun, you will see a recess cut into the steel just behind the ejector port. This is usually called a rollover notch. It is a common modification done to address just the problem you are seeing, which is a spinning case flipping around into the path of the returning slide. I dont know whether you already have one or not?
That spinning of the case is also affected by the strength of your recoil spring (a stiffer one will slow it down and throw cases more to the side). IF you have a full-size 1911, it will have a 16 lb spring standard, and going to an 18 lb. spring would be a good move. Wolfe is a standard, but I like the
Sprinco springs better. It is also affected by the length and the shape of the nose of the ejector. The long Commander-style ejectors find favor for getting a case out sooner in the cycle than the standard ejector, but that earlier interception of the case imparts more speed and spin to its ejection. Some guns prefer something in between. I dont know which ejector you have?
The other thing you will see in some guns is dented case mouths from the case mouths striking the lower edge of the ejection port on the inside. To get them the throw the case out at a slight upward angle, the modification to the Commander-style ejector nose below is common, and it may help move your cases out just differently enough to help, if you have this style ejector.
Adding a Wilson
SHOCK-BUFF or other recoil pad to the ejector spring guide can also affect ejection angle by stopping the whole slide a little sooner. These are inexpensive to try.
So, spring, SHOCK-BUFF, ejector carving, and of course you can get an ejector tension testing tool from Brownells if you still think that is the problem.
Nick