By location of this connector on the board, I still believe there's a hole somewhere under battery/sd card slot cover. Unfortunately my keywords don't return any good photos to confirm that.
Don't remember if it was tested or not - does the shutter bug persist after a software reboot triggered from ML?
It works for me on 5D3 for a different issue.
If the answer is negative (i.e. no shutter bug), I can prepare a workaround that would delay the startup process by 2-3 seconds.
Tried it and the it didn't work. If I follow your post -- the answer is positive, shutter-bug still present after a software reboot.
By the way, don't set Autorun on that script.