When you upload certain File types to Backbone (such as .dxf and .rul), they are displayed as MISC in the Files section. When you go to download these Files, they often appear in a new browser with errors.
We have plans to improve the handling of external Files, however in the interim, we recommend the following to get these Files to download:
1) On that tab, File → Save Page As (in Chrome). Make sure you don’t append the .txt extension to the filename.
2) Go back, right click on the Download link, and choose “Save Link As” (Chrome).