Created attachment 66471 [details]
the affected pdf file
The local public transportation map uses a custom font to display the line names (eg. S11). These are rounded rectangles, with the text cut out in the center.
The character is clipped at the right side by poppler/cairo, which means that the background shows through. See the attached PDF.
A good place to see it are the symbols for the S51, S52, S3 as they have a black background rectangle for the text that becomes visible. (eg. above "Germersheim")
Note that they are displayed correctly when they are rendered tilted. See the S52 at the central "Marktplatz" station.
Created attachment 66472 [details]
Screenshot with affected areas marked