Sounds like maybe the tight cable is causing stress that makes the needle touch the glass
The clearance is unfortunate over sensitive for that particular failure mode
Gm should have allowed an extra 1/32 or even 1/16 spacing for the needle because it seems to touch as soon as anything isn’t perfect like the needle aging and bending on its own even
Sometimes the speedo works on the bench and then installing it in dash also warps the whole assembly just enough to bind the needle as well
-s
