In the context of this stack overflow question I used the PDF Debugger to inspect the second page content stream of page 6 of the document provided as example, 2-30-SL-manual-DE.pdf, also attached to this issue.
The problem that question was about is caused by an invalid literal (neither string nor number) in some TJ instruction array argument. This literal indeed was visible in the hex view of the PDF debugger:
(See the "Tw" literals in the TJ arrays.)
But in the text view it was hidden: