setup for english, after running program once, resets to German.
This is confirmed to be a bug in version 1.0 on all systems with an English locale (all other locales will work). The problem occurs when the Preferences dialog is shown for the first time. On systems with an English locale, the setting in the listbox will default to German. So by pressing OK you switch to a German interface.
Will be fixed in next release.
Simple Workaround: Open the Preferences dialog once again and select English as program interface language. If currently German is active, the name of the corresponding menu entry is "Optionen/Einstellungen…".
Please state if this workaround was helpful. Thanks!