DXF export from SPIERSView is broken

[alanspencer]

Describe the bug
DXF export from SPIERSView appears to be broken

To Reproduce
Steps to reproduce the behavior:

1. Open a SPIERSView model
2. Export as a DXF file.
3. Try opening created file in a DXF file reader.

Expected behavior
DXF to open in external programs.

Additional context
Have checked though the created DXF file and it looks all in order. So not sure why the .DXF is not opening in DXF viewers,