Unable to open design file

There is a solution.

Alternative to Axiom FileFixer is to use 7-zip,SSViewer,Offvis and TeighaViewer:

1. Open DGN file using 7-zip File Manager. As the DGN file is structured storage(docfile) format and 7zip can show its contents.
2. In 7zip click Test archive. It will show if the file structure is correct.
3. If test shows error "Data error in 'Dgn-Md\#000000\Dgn~Mh'. File is broken" then open the damaged file using SSViewer.
4. And delete the broken stream Dgn-Md\#000000\Dgn~Mh. For interest you can check the stream contents by choosing Decoders->Zlib codec. DGN data is compressed using Zlib compression.
5. After that open and resave using Teigha Viewer. For some reason Teigha is able to reconstruct corrupted Model header stream without fatal error.

If 7zip doesn't open file then try to open DGN in Microsoft OffVis and choose Tools->Repair and Defragment. This could correct the DGN OLESS structure so it can be opened later inTeigha.

Another issue if shows error "Is not in a recognized format" then it may be missing DGN header:

1. Open DGN file using 7-zip File Manager. As the DGN file is structured storage(docfile) format and 7zip can show its contents.
2. In 7zip click Test archive. It will show if the file structure is correct.
3. If test shows ok  then open the damaged file using SSViewer.
4. And check if it is not missing Dgn~H and Dgn~Mf streams.
5. If streams are missing then export them from good file and then reimport using SSViewer (set Decoders->None when importing)

Shame that Bentley Systems doesn't provide tools to check and fix DGN file integrity. Security trough obscurity.

This seems to be bug in Microstation file handling when using files over network -https://communities.bentley.com/products/microstation/w/microstation__wiki/6935/microstation-file-access-issues-with-shared-network-drives

Lot of software products use Structured Storage format but only Microstation platform has this issue and mostly it corrupts model header stream so it could be bug in exception handling when connection to file is lost.

DEMO-bad-offvis-teigha.dgn

This happens when the file is corrupted. For me when 2 or more people try and open it in sharepoint while in file explorer view it gets corrupted. 

Opening design files over a cloud service like SharePoint would probably not be recommended. As well, multiple users opening the file at the same time I would not have thought was possible. Working within a document management system like ProjectWise might make a better workflow for sharing files.

FYI This discussion is over a year old but your inclusion is quite welcome. If you find this turns out to be an issue you wanted to have investigated you should probably consider posting a new item in the associated forum.