I just bought two of the cheap Chinese-made remote switches (a cheap clone of the Canon "Remote Switch RS-80N3") that are available for $9.98 on ebay. I tested both and found that one worked while the other seemed to have problems.
I opened the faulty unit and checked the switch and all the cable runs. Everything was OK. What I found, though, was that the plug didn't go quite far enough into the camera socket without pushing it rather hard.
The solution - I trimmed a little (a little more than 1/32") off the cable strain relief (the part 90-degrees from the plug itself), as that portion of the connector touches the camera body before the actual connector portion of the plug gets deep enough into the socket. The trimming of the strain relief allows the plug to go deeper into the socket. This little mod is all that was needed to make the switch quite reliable.
I have an original Canon RS-80N3, and there is a tremendous difference in the build quality. I bought these, though, so I can cut them up and extend the cable by 100 feet or so for taking bird and squirrel pictures.
