Windshield Wiper/washer problems of the 1998 GMC Envoy

Wiper malfunction with exact symptoms that the newer GMC SUV are having. Mechanics are using the same part on all vehicles and it occurs spiratically. Dealers are saying this controlling device is common to have this occur. The wiper motor sometimes just stop or change speed on it's own and it has be occuring from 96 to current and they only want to replace certain ones. I own a 98 GMC Envoy and this problem is happening. It doesn't happen all the time, but when it does it is dangerous to be driving in the vehicle especially traveling at higher speeds when it is raining.