Hi Dave,
When importing in 6.10.9 I get the same error without details. Then I tried in 7.5.1 and I get a more specific error:
Allthough I get this error I'm able to continue building the Consumed Web Service functionality in 7.5.1
Here a link to the Mendix documentation where you can see what is supported in xml structure and what not, anyAttribute is not supported by Mendix(yet).
https://docs.mendix.com/refguide/xml-schema-support