Hey 
When using the GET image endpoint to export an SVG, if you set the svg_include_id param to true the ID attribute may include whitespace if your node name has whitespace.
This is invalid - Document Structure — SVG 2
I think this issue is probably slightly broader than I initially described
Valid XML 1.0 names only include designated characters (letters, digits, and a few punctuation marks), and do not start with a digit, a full stop (.) character, or a hyphen-minus (-) character.
I think node names are mostly pulled through as is so there are probably a few more instances when translating the name of a node → an id attribute on an SVG are wrong.