Turn Signal problems of the 2003 Chevrolet Avalanche

The right turn signal assemble fell off my vehicle and had to be replaced- the housing bolts had broken off - I was informed this was not covered under warranty. 1 year and 3 months later I have the same problem again and was told that even though it had been replaced already at my expense since it was over a year I would have to pay for it again. How can the same thing happen? this is dangerous as the lamp and housing fell out and were dangling on my vehicle with a small wire as I drove, unaware of the problem until I had stopped.