I sued to get that same failure to chamber in my old Col Mark IV Series 70. I had the the extractor claw rounded and polished where the case rim contacts it on the way up. End of problem.
Yep, That's all it takes most of the time. The 1911 is a controlled round feed design so the case must get pushed up into the waiting extractor before the feed cycle really gets going. Smooth feed surfaces are a good thing. You might take some rounds and blacken the rim and head of the case and chamber it once (from a magazine) and look for marks where the marker was scraped off. Hey,Classic, I love your avatar photo. What a machine that is.