Writer not saving embedded .pdf images

I am using LO v5.3.5.2 on Windows 10.

When I try to embed pdf’s as images in a Writer document, it works at first. Then, as I’m typing up the rest of the document, and scroll up to proof-read, the images appear as black boxes (anchored objects) where the image used to be. I can still resize, etc, but the actual image is no longer there. I have turned off autosave, following advice in a different forum, to no avail.

This is a huge problem, since I routinely write scientific reports and absolutely must embed my data plots. Is this problem solved by upgrading to the latest version?

Possibly. I’m using Version: (x64) and tried pasting a PDF receipt into a writer .odt document and I was able to edit it without losing the image before saving it. The document was still intact after I reopened it after having saved it.

What is the source of your PDFs?