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If you see the problem with other lenses, then possibly the sensor is out of alignment, but if it is only with the one lens, then that points to a lens problem, with the mount or with internal elements. I had a similar problem with my 70-200, and it took 3 trips to NJ before they got it right, but it has been fine since.
More likely your lens mount is out of alignment or your 24-105 suffered a hard ride with UPS and elements drifted from true. My 70-200 4L became very soft on the left side after I ran a couple blocks with it around my neck. I cradled it much of the time as I ran but apparently there was enough trauma to knock the elements out of alignment. Canon fixed it but now I stow my gear in a bag before bolting.