Thanks for the help everyone.
And a special thanks to JudgeColt. Not only did you provide an education in the proper terms, you took the time to explain the cause and the possible fixes. I've had a few of these Colt revolvers apart in the past so I wasn't a complete stranger to disassembly. However, what I did find under that side plate really threw me. Somebody had been in there before me, and decided that wheel bearing grease was the way to solve the problem. Since that didn't work, they just buttoned it all back up and sold it through an auction site, to let the next person deal with it. After locating my tweezers, I set about cleaning and re-lubing. I get it all back together, and it still doesn't work. But everything is now nice and free, so I dig out the magnifying glass. I take a real close look at the locking bolt and spot a slight edge on the outside of the bolt. I grab a file and very very carefully break the edge. A quick wipe and lube and I lock the bolt into the cylinder, pull back on the hammer, and eureka, the cylinder starts rotating. It performs this function six times, then operates correctly in DA also. Locks up like a bank vault, and primer hits are dead nuts center.
So, now I have a Cobra that not only operates correctly, but I also know every piece of it by sight, if not by it's given name.
Colt repair center? "We don't need no stinkin' repair center"...lol.