Since 12.1 some PDFs don't show embedded images anymore.
Example from BMW site:
https://www.bmw.de/content/dam/bmw/...er_2018_online_01.pdf.asset.1537273370585.pdf
Example from BMW site:
https://www.bmw.de/content/dam/bmw/...er_2018_online_01.pdf.asset.1537273370585.pdf