Door problems of the 2005 Chevrolet Aveo

The entire lock of the driver side door fell inside the door when I tried to unlock my door. First I tried to fix the problem myself, but simply could not repair the problem. However, I researched the issue online and saw that many, many others have encountered the same problem before with this model. Naturally, because I would like to be able to lock my car door, I took it in and had it fixed for $160. The customer service rep just smirked when I told him what happened and said that we must've pushed the key in too hard "or something like that". I was not happy about the cost, but I paid. However, just two weeks later, the same problem occurred with the passenger side door, which I rarely unlock with the key. Apparently the dealer does not know what causes the problem. Fortunately I was able to fix it myself this time but had to take the door apart, but it was time consuming. It is vexing to me that Chevrolet must realize there is a problem, but does not seem to want to fix it.