Intermittent transmission

Recently the transmission in my 2006 Mercedes-Benz ML 350 has been intermittently sticking in gear, and when it does it won't come out unless I stop the car and re-start it. The issue seems to be electronic. It worries me as last week when turning right across heavy on-coming traffic it stuck in a high gear and just limped through the intersection. I have done some internet research and discovered that this model is subject to having a "limp home" mode issue. I have taken the car in to be repaired, but the problem couldn't be replicated. It is a huge safety issue as far as I am concerned. Can you best suggest how I should approach Mercedes to resolve this issue?