Hi, van6ogh.
That looks to me like the underlying drive had some kind of trouble. But -- in general, I wouldn't suggest using a "direct" DMG over a network like that. The problem is that it requires conversion, and conversion is
really slow, since all the data neeeds to be read and written again (see p21 of the User's Guide for a full description).
Instead, try following
these instructions for creating a sparse image. That'll go faster, and should work better. (Note, though, that if your network or "far-side" computer or device is troublesome, this could get errors too.)
Hope that helps!