I had a similar problem with my Rebel 30 footswitch. The plastic grommet that keeps the wire in place when it goes into the casing seems to be the culprit. It crimps the wire tightly and if there is pulling at that point, the wire can short out. Open up the footswitch by removing the screws. The grommet can be removed by squeezing the top and bottom of it, allowing it to slide out of the hole.
I cut out about an inch of the wire, then stripped both ends. There are 3 wires: red, white, and ground. I soldered the leads together, taped them off, secured the wire back in the grommet, and put the footswitch back together. It works fine now.
I do take special care not to put any undue strain where the cord goes into the switch when I wrap up the cord to put it in my case.
If I may be so bold to make a suggestion to Egnater, my experience is that I have much better luck with footswitches that have an input jack to plug a cord from it to the amp, instead of hardwired ones.