PDF images got spontaneously compressed

I have an Impress file with many PDF images in it. When I exported the file to PDF, all the embedded PDF images used to work fine. But now, some of them get compressed (looks like JPEG). Why?

Version: on Linux

  • Did you export from the file menu… Export as PDF?
  • Had you chosen Lossless compression?

If each answer is YES so provide a sample file.

Yes for both.

ODP sample: sample.odp - Google Drive

PDF sample: sample.pdf - Google Drive

Figures in slides 1 and 5 are the only ones that worked fine. (And they were the last ones to be inserted.)

I think they got converted in the file itself, not during export.

My suggestion: Open the PDF with Draw, and copy from there the images to paste into Impress.