this topic is now nearly one year old and I still have the same issues that @jtucker has.
I have created my business logo in Inkscape and opened the SVG file in Affinity Designer 1.5.1 and the position of the elements is not as they are supposed to be. In Inkscape the same file looks great or even in the Mac preview. But AD also throws out some parts.
I also have that issue with my business card template that I created in Photoshop and stored as an PSD file, AD is throwing out (or not showing) elements.
I deleted Inkscape and terminated the Adobe Abo so I do not have both apps available, but the Mac preview shows the files without any issue.
Is there something that I can or have to do @MEB?