DXF export error with embedded script

[M8-Rery]

I created a SVG-file with a 3rd-party application "Skeinforge" (from RepRap 3D-printers), and opened it in Inkscape. This works fine, and all is displayed correctly.

However, when trying to export as DXF I get the error shown below from the export module.
After playing around, I found it doesn't matter what the encoding in the file header or the export dialog is set to. The problem is the degree-sign-character in the .svg file at line 174, column 69. If you replace it with something else, the export works.

Now, why does opening in Inkscape not suffer from this bug? As a user, I'm under the impression everything is OK, so a re-save should produce a SVG-compliant file. (It doesn't in this case.)
Is there a way to save a "clean" SVG, so the problem could be solved by re-saving in native Inkscape-SVG?

I attached an file that shows the behavior. I does not contain any visible geometry, however export fails.

Traceback (most recent call last):

  File "dxf_outlines.py", line 345, in <module>
    e.affect()
  File "C:\Inkscape\share\extensions\inkex.py", line 264, in affect
    self.parse()
  File "C:\Inkscape\share\extensions\inkex.py", line 187, in parse
    self.document = etree.parse(stream, parser=p)
  File "lxml.etree.pyx", line 2692, in lxml.etree.parse (src/lxml/lxml.etree.c:49594)
  File "parser.pxi", line 1522, in lxml.etree._parseDocument (src/lxml/lxml.etree.c:71582)
  File "parser.pxi", line 1552, in lxml.etree._parseFilelikeDocument (src/lxml/lxml.etree.c:71892)
  File "parser.pxi", line 1435, in lxml.etree._parseDocFromFilelike (src/lxml/lxml.etree.c:70807)
  File "parser.pxi", line 997, in lxml.etree._BaseParser._parseDocFromFilelike (src/lxml/lxml.etree.c:67948)
  File "parser.pxi", line 539, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:63824)
  File "parser.pxi", line 625, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:64745)
  File "parser.pxi", line 565, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:64088)
lxml.etree.XMLSyntaxError: Input is not proper UTF-8, indicate encoding !
Bytes: 0xFF 0x27 0x29 0x3B, line 174, column 69