The toggle switch is failing intermittantly

I suppose that with "toggle" you mean what Canon calls the multi-controller, the directional button that is next to the upper right hand corner of the LCD screen.

The most likely cause of the problem you're having is that the response of the control has degraded due to dust, dirt, or sweat getting in. Since the control is already quite fiddly when it does work as it should (at least in my opinion or maybe my thumb is just too big), when this button starts acting flaky it could be a major pain in the backside.

Regrettably there is no ready-made guide available for cleaning or replacing the controller, but the most difficult part of the operation is the removal of the rear part of the camera's shell, which is shown here.

Once you have the rear shell off, you will need to remove the metal screen that covers the wheel control and the multi-controller which look like they are a single assembly. Removal should be relatively straightforward but take care not to damage the attached ribbon cable. Once you have the control assembly out, you can then proceed to remove any crud with a q-tip and electronics grade (i.e. pure) isopropyl alcohol. A small drop of contact cleaner (use a proper contact cleaner, not WD-40!) applied between the control plunger and the housing, followed by actuating the control a number of times, will in most cases take care of corroded switch contacts - unless the control is properly worn or defective, in this case it will need replacement. It doesn't hurt to check the control's solder connections for corrosion or cracks, if necessary a miniature soldering iron with a fine tip can be used to rework the solder joints.