"think" or know? There's one thing I do know and that is the number of times a spring is compressed directly coorelates to spring fatigue. If you'll notice that HK makes their springs from the same material that Colt does (merely at at higher spring strength), and Colt springs are lucky to last 5000 rounds of optimal performance before starting to degrade. The spring in question here IS degrading by this point. Add in a fatigued ejector spring and things show even worse.
I recently saw a guys gun with 10K rounds down the pipe, and while he wasn't having failures yet, the rubber buffer cap on the end of the buffer itself was squashed, cracked, and starting to mushroom. A quick replacement of the action spring and all the springs in the BCG and his gun was back to where it should have been (he also of course replaced the rubber buffer).
Remember what I keep saying about excessive internal wear? Just because the gun "works" doesn't mean it's working *right*.
And let me tell ya, for all the great things I've heard about torture tests and the like, the one thing they never mention is regular spring meintinence because it's considered normal to change springs at various cycles in a machines life. When they say with no "parts" replacement, I can easily see that. Meaning no bolts have broken, the fireing pin, extractor, ejector, etc. etc. etc. are all fine. Saying a gun made 25,000 rounds without replacing a good majority of the srpings would be like me saying I ran my car for 25,000 miles without ever changing or adding oil to my engine. Sure the gun is good, but the springs simply are not that capable.
So, what I said still stands. Look at the action spring and the ejector spring in specific. replace as necessary and if that doesn't change the ejection pattern, then i'd start looking elsewhere.
P.S. you do know that ejection chart is virtually universally despised on M4C.net, right?