Great, I missed that one.. search was probably too limited.
Although neither TSB doesn’t explain what shims are correcting.
The additional info on door side, very helpful, but interesting... adding 2mm to inside door link mount essentially places the door link’s travel point back to initial point... adding 2mm on door moves link back 2mm, adding 2mm to link mount moves it away from door removing the 2mm door mount’s depth change.

I first thought the TSB to add 2mm on door side was pushing link back a bit to provide a small amount of additional clearance to allow a little more inertia before encountering resistance. But 2mm to inside door mount removes the adjusted depth and simply moves the whole assembly back 2mm which I don’t understand what that corrects.

I’ll give 1 or both a try... but as of today, the 3 times used, it’s worked great! Go Figure!

White lithium grease works for the links.

Haven’t pulled door Panel to closely inspect or attempt to isolate... just my quick assessment after a spray of white lithium grease didn’t quite it down. Are the links a common point of noise? Isn’t high on my list to correct, just thought I’d inquire if many have experienced & if correction. Thought when I had panels off for some other need, I’d look a little closer.

That’s back on par to my original assessment to improve inertia... moving it back 2mm towards mount for clearance or less tension. Thus 4mm might... would have to look, help more, depending on location of hump’s peaks.

That confuses the 2nd suggested shim inside door, shimming the internal mount 2mm moves the mount away from external body link mount, thus canceling out the 2mm setback and placing hump back to original point on the link mount asmb, the whole assembly moves reward 2mm (2mm link, 2 mm Mount). If moved mount 2mm (reduced) towards external mount, it would provide 4mm offset change total.

Not a major ordeal, just saw the inconsistency in changing Link Hump position... maybe moving the whole assembly back is accomplishing something I’m not following since I haven’t taken it apart yet.

Follow up thought... is the replacement link an assembly: link arm and mount (with rollers, and tension springs)?
Haven’t checked, possible still available GM part?

Check our common part numbers thread.

Had same problem with back doors on the wife’s panel when we got it 5 years ago. Took it
to my friend who owns a hotrod shop and had him install aftermarket poppers. Now the doors
open with no issues. Just have to close the door harder due to spring pressure but it’s easier to
do that than be aggravated with them not opening.