Looks like I have the same tripod so I have just checked the clamp bolt , sorry to hear your lens got damaged.
As Manfrotto own Gitzo now and have done for several years you would think that they would sort this problem out . A simple two or three locating grub screws would be a simple fix , maybe even the more handy of us could drill and tap these ourselves.
As Manfrotto own Gitzo now and have done for several years you would think that they would sort this problem out . A simple two or three locating grub screws would be a simple fix , maybe even the more handy of us could drill and tap these ourselves.