FOP / PDF: Font invisible (color white?) and download action fails in Chrome browser

[Hacont]

Reproduction

1.) Open koalixcrm with Chrome browser
2.) Create your personal template for invoices with the predefined template and font configs.
3.) Create a contract with an invoice
4.) Select the invoice and execute action "Create PDF"

==>
The PDF is generated in Chrome browser with the predefined templates and font configs, the document is displayed directly in the browser. The borders of the tables for the positions and the total calculations are visible. The logo is visible. The text in contrast is invisible - probably white. You are able to copy the whole document and paste it e.g. into a word document and you see the whole text.

5.) Download the PDF within the Acrobat Plugin

==>
A popup to choose the download directory is displayed, but the PDF is not recognized as PDF (Proposition for the document name is only "Download") and if the user clicks on Save, the download fails.

Prerequisites

- koalixCRM is opened in Chrome browser (Version 63.0.3239.132 (64-Bit))

[Hacont]

If the Chrome browser is configured to directly download the PDF instead of displaying it, the document is stored correctly (but with the ugly name "Download.pdf") and can be opened with visible texts with Reader on Windows. The problem seems to be Chrome PDF Reader related.