I am running a DA 11 speed chain, currently at about 4900 miles of relatively clean, lub'ed use over Baltimore County roads.  I weekly measure the chain using a Park CC3.2 at a couple of different links.  When I checked yesterday the 0.5% did not slip in.  I spun the crank a half turn and remeasured.  The 0.5% went in.  Spun the crank another half turn and the 0.5% did not go in.

I then checked the entire chain and found one section of about 20 consecutive links at 0.5% wear (but not 0.75%) and all the other links were under 0.5%.
I had always assumed a chain on a non-fixie would wear uniformly.  So what is actual wear here, do I replaced the chain a little early?
What chance that this is a defective chain from the factory and that 10 link section was always out of spec.  Who checks every link on a new chain?