While Netsblox doesn't allow you to save a project with a period in it, It seems you can save a project with a slash or question mark. When you try to share a project with either of these characters, or if you try to delete the project Netsblox crashes. I made a short video to demonstrate: https://youtu.be/I0fvU5vSDmI
I can't seem to duplicate this error in Snap, if that helps.
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!