2.0 tdi sline dsg gearbox cutting out

Hi people, as the title suggests my dsg gearbox has staple in the last few weeks twice whilst in reverse. If you turn car off then on again it's fine today however when in d and car is still cold and stationary with foot on brake there is a lot of exhaust fumes is this some thing that should cause concern. Any ideas what could cause the cut out. It's due. For a gearbox filter and oil change soon 120000 miles.

Thanks in advance.