« on: September 13, 2014, 03:35:40 AM »
As long as there's no front to back movement, I wouldn't worry about the mount. The weather seal gasket not making contact with the lens mount is definitely a concern. Has the gasket been deformed or torn? Do you have access to another weather sealed lens to see if its gasket functions normally with your camera? Do you get the same result when you mount your lens on a different camera? It's kind of unusual for an undamaged gasket to not make contact. I also have both the 24-105 and the 70-200ll and I find the 70-200 to be noticeably sharper than the 24-105 at similar apertures. It might be a good idea to send your camera + lens to Canon for service.