Hazard Flashing Warning Light Unit problems of the 2004 GMC Sierra 1500

My 2004 GMC sierra would light all four turn signals when the left turn signal was applied, as if the hazard lights were on. Took it to dealer and they said they had never seen anything like it before. Paid almost 200 dollars to get it looked at and fixed. After going home, I see that other sierra users have the same problem. More shocking, I see that gm had the exact same problems with some envoys, barbados, trailblazers, and others, and performed a safety recall at no charge. It is outrageous that all vehicle owners with these problems were not notified and the faulty components replaced. Have been trying to get in touch with gm about this and they have yet to send me anything but carbon-copy e-mails and runarounds.