Exported XML does not look identical to original XML
You imported an XML file that had a lot of whitespaces, line breaks, etc. in it. Upon export, the file does not look identical.
Actually, this is not a problem though many people find it problematic. For most file formats, formatting is crucial, but not for XML. XML does not care about spaces and line breaks, because XML input is not for human reading but for computers.
As the XML specification states:
In editing XML documents, it is often convenient to use "whitespace" (spaces, tabs, and blank lines) to set apart the markup for greater readability. Such whitespace is typically not intended for inclusion in the delivered version of the document. On the other hand, "significant" whitespace that should be preserved in the delivered version is common, for example in poetry and source code.
If you still want to care about that whitespaces, you can. When you are setting up an XML filter configuration, you can select Whitespace handling for each and every tag. Here select "Preserve" for the value, rather than "Inherit". XML source files can be set to preserve all whitespaces, in that case memoQ's default filter preserves whitespaces. However, if this isn't stipulated in the source file, memoQ does not necessarily keep the whitespaces, unless you explicitly set it up.