Bug likley caused by Calibre book reader dependency package missing during assembly

I am using

• Arch 6.9.1, latest version
• Calibre 7.10.0-2, latest version

Everything on my system is fully up to date.

However, epub doc export to pdf, within the Calibre package, was occurring with significant errors, and has done so for approximately the previous 6 months, I switched to the native package from the origin developers site, which does not have this issue

sudo -v && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin

The problem with the Arch Calibre package is that, epub doc export to pdf, within the package, currently occurs with significant errors, as follows

• rendered pdf text in the output pdf is not rendered properly, the problem being significant to the extent that pdf book exports are all un-useable, because they were unreadable.
• So there is something wrong with the way the Arch package is built, I suspect a dependency in pdf creation is missing.
• More specifically, the issue is that
  • some layers of the pdf file are in transparent layers, and cannot be seen with any pdf viewer.
  • all pdf text is present, in the exported pdf's, which can be proven by copying blocks of random text in any exported pdf doc, and then pasting it into a text viewer. So the issue is not the presence of the text in the pdf doc, the issue is the transparency of some layers of text in the pdf doc.
  • all epub files converted to pdf have this problem

An example of this problem, with transparent layers for letters v and h and other letters, is shown here, in this screenshot jpg image file https://drive.google.com/file/d/1AdHPQK_sEkpznh99yW4t-FhoCPssIpYa/edit

How to re-produce the flawed pdf's ?

Use the ebook-convert utility supplied with the Arch compiled Calibre. Here is my one-liner script to produce a flawed pdf:

ebook-convert \
book_name.epub \
book_name.pdf \
--embed-all-fonts \
--paper-size=a4 \
--pdf-add-toc \
--pdf-page-numbers \
--pdf-sans-family \
--pretty-print