First test is to do a single round mag load, charge and fire the round, and confirm that the bolt is locking back on the bolt catch after being fired (cycle function test).

If it passes this test, then move onto extractor if the case is being dropped from the bolt face before end of rearward stoke.

Also confirm that that the mag(s) is in working order (read Working USGI).  The cheaper clone mags do tend to fountain the rounds at the slightest impact, and what you may think is the extractor dropping the round, could be the top round in the mag being flung out as the B/C clears the mag, and this top mag round knocking the case from the bolt face.

Note: the insert in the extractor spring is normal.  Its function is not to add tension to the spring, but to prevent the spring from collapsing sideways under tension.  The color of the insert is normally a marker for the strength of the spring, and had the spring been a Colt heaver unit, the insert would have been Black.  

When in doubt, start swapping parts with those of known quality and working conditon.