Out of two Xml files with the same contents, only one can be opened

I have saved a very simple Xml file from Inkscape 0.91 (r13725) in Windows 7 x64. When I load this Xml file by means of the XmlDocument class in .NET and save it again, another SVG file is created.

https://www.corefiling.com/opensource/xmldiff.html confirms the original and the copied file have (semantically) the same contents (except for Inkscape writing "UTF-8" when .NET writes "utf-8" into the header, but that doesn't change anything about the problem described below).*

The original file opens flawlessly in Inkscape. The copied file cannot be opened, as Inkscape crashes with the message "Inkscape encountered an internal error and will close now."

I suspect Inkscape is chocking on a valid file, but if this is not a bug, then there must be at least some very obscure issue in the copied file that Microsoft's XML engine can handle while Inkscape fails on it, in which case I consider the uninformative and hence unhelpful error message a bug.

I have attached the following files:

- a.svg: the original file as saved by Inkscape (can be opened in Inkscape)
- b.svg: the copied file as output by .NET (cannot be opened in Inkscape)
- copyxml.cs: The source code of a tiny C# program that, when run in the same directory as a.svg, will copy a.svg to b.svg

* On a side note: https://validator.w3.org/#validate_by_upload says both the original (Inkscape-saved) and the copied file are invalid SVG because allegedly, <flowRoot> elements must not be children of <g> elements. That notwithstanding, both files are well-formed XML according to http://www.xmlvalidation.com/ .