This was a fairly inexpensive lens and I doubt if Canon could repair it in an economically feasible manner.
The switch isn't a momentary/spring loaded type so the "guts" of it should stay in position once moved.
You could move into place and then use a small piece of plumber's putty to prevent it from moving out of place due to shock/vibration and this would also provide some protection to this area that would normally be covered by the switch lever.
Plumber's putty is useful stuff for a lot of temporary applications. It removes easily without residue and is non-conductive. I found that when shooting with my EF-300 f2.8 lens as part of a two camera combination, the positioning of that lens and 1DX II body made it easy to accidentally bump the lens switch from AF to man when quickly grabbing the camera. I started putting a small ball of plumber's putty in that area before game time to prevent accidental movement and it works very well and removes easily after the game when I am putting up the gear.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
