@RbnJrg,
A follow-up question... Are .svgs valid in any format other than epub?
I tried to create an AZW3 and KEPUB by calibre-converting your SVG sample epub. Both have empty spaces where some of the SVG images and/or SVG text should be. Both are 'wrong' in different ways. It's hard to know whether the root of the problem is with the AZW3/KEPUB formats, the conversion process or the calibre Viewer or even a combination of all three