There is a bug in Inkscape 1.2 that could destroy gradients, clips and clones in one's drawing, but one would only notice it happened after saving the file and then later opening it again. To work around the bug do NOT use copy-paste while having the Export dialog open! The bug will be fixed in Inkscape 1.2.1.
Another bug prevents filtered objects or embedded images on any page of the document other than the first one from being exported to PDF. As a workaround, you can use layers instead of pages, or move the page content to the first page before exporting.