Uli Becker wrote:

I tested your project and it works fine here. Which build have you
installed?
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Of course I have Build 5 installed.

I found out that it is a problem with Internet Explorer 10 which runs on my Windows 8.0 machine (and is used for dispaying the internal web browser output). No problem using Firefox or Chrome. No problem with Internet Explorer 11 running on my Windows 7 Laptop.
Strange...