This was found in version 1.23 (git >= 8855c14) with 'printing-with-scintilla'.
When printing with line numbers, a vertical line is added between the line number and the line of text. This line appears at what seems to be the correct location when viewed in print preview and when the document is sent to a PDF file. But when hard-copy output is chosen, the vertical line is drawn to the left of the right-most digit. For example, at line 123, the line appears between the 2 and the 3.