ML350Cdi BE now replaced, E220 2013MY just for a bit.....
I found on both MB and Audi systems the conditions have to be perfect, and I mean PERFECT for the systems to operate as advertised, and even when they do it is so slow as to be an embaressment in busy traffic, much easier to park manually.
Cannot say I am much good with it on my S320,but at the bottom of the screen it has the little pictures of either turning around a corner or entering a parking space,choosing one of them might help or not,ain't technology great.