Ryobi ECW-1841 Electric saw micro switches keep failing?

I own a Ryobi ECW-1841 electric chain saw. There are 2 microswitches in the handle activated when the trigger is pressed. One of the micro switches keeps failing (left hand side switch when viewed from above). I have gone through 3 new micro switches now. I suspect a wiring fault somewhere that places an overload on the switch?? Anyone any ideas or come across this fault before? If I cannot find an answer to this I may as well bin the chainsaw as repair costs will be high.

Robert webb
January 2008