I'm experiencing an issue where my SVG graphics are missing elements when displayed outside of Inkscape. The Inkscape image is (including the document border):
However, I've tried displaying this in Firefox, Chromium and Anki and they all show an identical output:
I've done some searching for this, but most of the reported issues relate to problems with fonts, which isn't my issue (I converted them to paths). I've also tried different svg output file formats (plain and optimized with various settings, including max decimal places) but nothing seems to change the result.
The missing components (I'm using a custom symbol library) have displayed fine in other schematics and I haven't been able to figure out any pattern as to when it works. I'm using the "default px" template and Inkscape version 0.92.2 on ArchLinux with KDE Plasma.
Here's a link to the file on DropBox.