I also am having this craziness happening when exporting to SVG. In my case, the export of a particular important file is shrinking everything by 25%. I have tried setting the export DPI to 72, 96, and 300, with the view box option turned off, and every time the objects in the exported SVG are shrunk by 25%. Example: a rectangle that is 8 inches in Designer is 6 inches after SVG export. This is pretty weird.
I don't mean to suggest a fix — that's up to your wisdom — but something very randomly buggy is going on, given how the errors are all over the place in this discussion.
