What I mean is that I addressed how often a tight link occurs and how to diagnose it. The primary reason to pretty much eliminate that as a factor is that the problem remained across two chains, as I also noted. The symptoms match what would happen with a freehub whose pawls are no longer operating properly, and the freehub is one part of the drivetrain that has not been replaced. Actually, the OP could try flushing it out before resorting to replacement.