Hello Steffen,
thank you for your response. Yes, I receive a Mac OS crash report for python when I import nest, under this link you find a text file with the output of the crash report:
https://www.dropbox.com/s/3g8g4kr24d5ivha/nest%20import%20-%20python%20crash...
I hope this contains any clue to solve the issue.
Best regards, Michael