general problems of the 2005 Cadillac CTS

Whenever it gets cold and/or snows, the left rear door of my car opens without warning, then will not remain closed. This is the third time this has occurred since I have owned the vehicle. The first time I returned to Cadillac, it closed when I arrived at the dealer, the second time my son was able to close the door. This last incident, I could not get the door to remain closed, I took it to the dealer, who explained to me there is nothing that can be done to fix this, they follow the guidelines set forth by gm, which is to apply an oil that will absorb the moisture in the doors mechanism. While at the dealer, there were 3 other people with the same complaint. This is a dangerous condition that can cause harm, the first time it happened I had my 2 yr. Grandson in the back seat. Gm should notify its customers that this is a defect of the vehicle. The service person informed me that there is nothing he can do about it, the only solution is to return to the dealer each time this occurs and have them lubricate the door.