NetsBlox has been updated to version 1.8.0. Most notably this includes:
In projects using multiple roles, "Save" has been replaced with "Save Role" to make it clear that it only saves the current role that you are editing (any other users on different roles will not be automatically saved).
Added historical stock price information to IEXTrading service
Miscellaneous bug fixes and improvements
For more detailed information, check out the release notes!
What error are you seeing when you try to export it locally? It wouldn't hurt to try the dev site but I can't think of any changes that would be relevant to that error.
The main site, editor.netsblox.org is the latest release on GitHub and is vetted so it should be stable. dev.netsblox.org is the development site and loosely follows the main branch on GitHub. As a result, it has the latest features and early versions of upcoming services. Since it tracks the main branch, it also gets the bug fixes faster, too :) (even if it is generally considered less stable).
Unfortunately, I still don't follow. Are you trying to open the assignments from here? If so, I would recommend downloading the xml file from the corresponding assignment directory (this one is an example) and then importing it into NetsBlox using the "Import..." menu item from the file dropdown.
If that doesn't work (and is in fact what you are trying to do), feel free to post screenshots to help show the error you are encountering!