REG->5.12? Qt5.12 ignores settings for QPrinter and always produces PDF-documents in format: "US-Letter" portrait

I have a program which printed directly to a pdf-file in portrait- or landscape-orientation using QPrinter. Everything worked perfectly with PySide2 v5.11(also with PyQt5 v5.11.2) and Qt5 v5.11.2.
But now, after update to Qt5.12 and PySide2 v5.12 (or pyqt5.11.3), whitout any code-changes, I always get documents in format "us-letter" in portrait-orientation.

I have a minimal working-example and some pdf-files to illustrate this here: https://www.dropbox.com/sh/feve6ubvy...5zGdQI9ra?dl=0
(I had to remove names in two of the documents with LibreOffice Draw. Thus, the specs say that they are generated by LibreOffice instead of Qt5.12.)

In my example scripts, I let python print the printer-settings and they are correct, but the generated output is wrong.