Hi Christoph, I have exactly the same issue. I also find if carry on typing it maxes to 4000.
The work around I've been using as I test this is to type the resolution in notepad and then copy and past into the field.
I've been testing the ability to export whole sheets and have also found that the export fails if you add more than 7 sheets. I'm still testing it to see if there is something specific the failure relates to.