Grasping for ideas at this point So to toss in a few more combobbolators. Are all the bars doing this on the same saw, or more than one powerhead? My odd dimension of thought is if it is one saw then possibly(unlikely) the chain is shy of oil or a poor grade of bar oil (Post #8) and then chain starts to fight in its' rivets and bind up from lack of flexibility (post #12) . Is the chain loose/flexible in the rivets after it has ran? I think the Air Filter and Combobbolator are merely masking the real culprit/Issue.
The 2nd bar pic shows a long stretch of damage that appears like iron grating across iron and indicative to a very dry surface, even though the damage leads you to think it is chain chatter.
Like the first word in the post says "GRASPING"