Holden Viva transmission issues

Our 2008 Holden Viva Wagon had barely done 10,000 km when the transmission slipped out of gear when turning a corner. My wife had to glide to a stop and it was just luck she wasn't hit. We were informed by Holden that the transmission had to be replaced. That was fine, until the same thing happened to someone else I know. My subsequent research suggested that it happens a lot. Even the mechanic at the dealership said it wasn't the first he had seen. I am concerned that the new transmission has the same fault and could fail again, and how can I be sure that it has even been replaced? I have contacted all and sundry at the dealership to at least provide some documentation about the replacement, but to no avail. Do you have any advice?