The tray was redesigned early and replacement of the part is very easy. The shape has been modified very slightly to ensure that the button rotates far enough to prevent this issue.
If you are in the field already the best option I’d say would be to set the focus to the thumb lever and use this to focus. That way, the AF/M function on the camera is superfluous.
If you don’t want to do that, a quick fix until you can have the part replaced would be to build up the part which connects to the dial using electrical tape or similar.