I did some further investigation.
The following conditions apply to my system:
- Windows 10 (German Language)
- Documents folder moved to D:\Dokumente (using the properties of the documents folder)
I monitored the Spirit Settings process with Procmon (SysInternals). There I can see, that the Settings tool creates a new PDF-file in my D:\Dokumente folder, but then tries to open C:\Dokumente\spirit-log-....pdf. The drive letter changes from D to C. On C the folder Dokumente and the logfile do not exist. But if I look manually into my documents folder on D, there the logfile exists and I am able to open it using the Explorer. It just does not work from the Spirit Settings tool.