I tried resetting the camera position in Layout, restarting layout, and always got the same result.
My workaround was to open the PDF in Illustrator, and insert a screenshot.
It looks like the fix for this won’t come very soon. The workaround is to change the graphics engine to the classic one, then the export comes out looking correct.
Can I model using new graphics, then switch just for the export?
This is a better workaround than I used, which involved swapping images out in the exported PDF…