Reminds me of when I went on business trip of several weeks to Sweden from California. The Swedes spoke English reasonably well. I then went to Scotland for vacation and had a much harder time understanding their dialect than I did with the Swedes.
For me as a non-native speaker of English and German, this is quite normal - I mostly have an easier time understanding other non-native speakers since they usually use "international" dialect/pidgin, speak slower and usually articulate more distinctly.
