Very interesting reading, I have a completely standard 97 about 4 years old. Yes it is twangy and the ABT link buzzes like a wasp in a can when shot, but mine has approximately 1/4" of free play on the cocking lever when released (have not taken it out the stock to measure how much this is at the compression tube) but definitely has free play.
How about using a thin plastic spacer 0.1 - 0.2mm at the front of the compression tube to create free play and see if the problem goes away ?
Could it be a problem caused by the breech seal ?
Just thoughts, having not experienced it personally.