Unless it doesn’t, and then it is us hunting down something when you could quickly provide an example that can be immediately examined. For example, a paste of an SVG from Sketch and on macOS 10.15 doesn’t reproduce this at all. It was not immediately clear from the post what the screenshots were about, but much more evident in the document. Please always provide reproduction documents and steps to reproduce when possible. We are trying to save time and provide accurate solutions when asking for a document - your time included so there is less back-and-forth on an issue.
In this case, the issue with the question mark appears to be resolved in macOS 10.15 for me (and I would also guess it is resolved on 10.14 from what I recall about it). But now that I see the document, it is probably because the scene thumbnail creator didn’t have correct access to the background image paste file.
As for the single line on the side, this is an artifact of the fact that Vector Shapes use SVG repeating patterns as a background image, and the SVG image for this pattern has non integral width/height/viewport size that isn’t a perfect fit in the integral pixel based element.
If you were to change the pasted SVG to use pixels, it would work:
<svg version="1.0" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="322.2px"
height="220.5px" viewBox="0 0 322.2 220.5" style="enable-background:new 0 0 322.2 220.5;" xml:space="preserve">
<svg version="1.0" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="322px"
height="220px" viewBox="0 0 322 220" style="enable-background:new 0 0 322 220;" xml:space="preserve">
I’ve filed a bug on our tracker to see if this can be improved.