A few years ago a girl at my English department at a German university had her final oral exam to become a teacher. Unfortunately this girl spoke English with a very heavy Swabian (southern German) accent/dialect. The external examiner who was from northern Germany was close to failing her. To be honest her English was very difficult to understand. And only after the girl’s supervisor insisted that she’ll only teach English in southern German schools (because that’s how the teacher program used to work in Germany) was the external willing to let her pass with a 4 (the worst possible grade he could give her without failing her).
On a personal level, I’ve lived in the US and UK for about 10 years now but as a German I occasionally still get the v/w distinction wrong. Especially when I’m tired. Saying vikipedia instead of wikipedia always gets a few good laughs in the office.