I have an issue with a certain PDF file where some elements of the image are not imported and don't appear in Inkscape.

Opening the PDF in a web browser, PDF viewer, or importing into GIMP have no problems.

I have tried with the latest AppImage I could find (build ee3ba9c) and the problem persists. The PDF even renders correctly on the import preview screen, but still isn't complete when loaded into Inkscape.

I have attached screenshots showing the difference between preview and import, and the original file which causes this issue.

No clue why the rendering fails as all elements are there but wrong style is applied:

SVG expects every path to have two or more nodes. The missing circles are paths with one node and a heavy line weight producing a circle in my pdf viewer (MacOS Preview). Confused, Inkscape doesn't know what to do with these and therefore ignores them. Here's a manual workaround.

Select one of these single nodes and examine it in the XML editor [Edit > XML Editor...].  <path id="path452">
The value of the "d" attribute defines the nodes and lines that make the path.  M -401.2257,-248.3161 Z
This tells Inkscape to move M to the first coordinate -401.2257,-248.3161 and then close the path Z.
Change this attribute value to  M -401.2257,-248.3161 -401.2257,-248.3161
This tells Inkscape to move M to the first coordinate -401.2257,-248.3161 and draw a line to the second coordinate -401.2257,-248.3161 which happens to be the same as the first. This is an open path.

This is good enough for your case with only six orphaned nodes. For greater numbers, use a text editor to find and replace the lonely dots. Ideally Inkscape would handle these when importing a pdf file.

Polygon

No clue why the rendering fails as all elements are there but wrong style is applied

The small white circles are separate elements and are meant to be there. It's the larger black circles that don't show up.

Paddy_CAD

SVG expects every path to have two or more nodes. The missing circles are paths with one node and a heavy line weight producing a cicle in my pdf viewer (MacOS Preview). Confused, Inkscape doesn't know what to do with these and therefore ignores them. Here's a manual workaround.

Select one of these single nodes and examine it in the XML editor [Edit > XML Editor...].  <path id="path452">
The value of the "d" attribute defines the nodes and lines that make the path.  M -401.2257,-248.3161 Z
This tells Inkscape to move M to the first coordinate -401.2257,-248.3161 and then close the path Z.
Change this attribute value to  M -401.2257,-248.3161 -401.2257,-248.3161
This tells Inkscape to move M to the first coordinate -401.2257,-248.3161 and draw a line to the second coordinate -401.2257,-248.3161 which happens to be the same as the first. This is an open path.

This is good enough for your case with only six orphaned nodes. For greater numbers, use a text editor to find and replace the lonely dots. Ideally Inkscape would handle these when importing a pdf file.

Thanks! Doing this worked. Actually there were 13 problematic points in the file.

Funny thing is even though they now show up, I can't select them by clicking on them. I have to draw a selection box around them instead, and then shift-click to deselect the white dot in the center.

[Path > Stroke to Path] changes these unselectable dots into selectable shapes.