Ejection issues are much different than extraction issues. As you said you are having ejection issues, I will only deal with that. Although the two issues are often related, I try to deal with each separately. Here is what I check first for ejection issues.
1. If the extractor has too much pressure, it pushes the casing so hard onto the inside of the bolt, that the additional pressure/friction prevents the case from making it out of the bolt in time while the rifle is cycling. Make sure that your extractor doesn't have too much pressure onto the case.
2. Check the extractor for burrs that cause the casing to hang up. Also insure that the radius on the ejector matches up with the casing's extractor rim. Manufacturing issues occasionally happen. A broken or cracked extractor can cause lotsa problems.
3. Make sure the gas system is working right. The gas key has to be tight, bolts staked properly, gas rings staggered, and not worn. Very small issues with the gas system, cause large issues in functioning. Also make sure that the gas system from the gas block rearward is working right, not leaking, or worn.
4. Check to insure that the ejector has sufficient power, and operates smoothly. If you put an empty casing into the bolt as it would appear in the chamber, then let it go, the ejector should have enough force to flip it out of the bolt sort of like you would toss a coin using your thumbnail.
5. Make sure there aren't any burrs or cracks on the bolt lugs, or the lugs on the barrel extension. These would cause the rifle to not operate smoothly.
6. If the rifle is overgassed, it works too fast for the extraction, ejection, reload cycle to happen properly.
7. Insure that the proper recoil spring is in the butt stock. If you have an carbine spring in a rifle butt stock, or the reverse, that will certainly cause problems.
8. Consider playing around with different weights of recoil buffers. Sometimes, a heavier or lighter buffer solves the problem.
These are the ejection issues I would check first. Extraction issues have a different check list, but usually extraction is pressure related.