Main window cannot minimize correctly to the system tray

I checked in the settings the option "Minimize to the system tray". At the first start, the main window is open. When I click on the minimize button, the window go normally in the system tray. Then, I click twice on the system tray icon, the window is restored. At this time, if I click the minimize button, the window is reduced in the right bottom of the screen (Radegast icon is always available in the system tray). If I try to restore the window from the contextual window menu, the window appears normally, but minimize and restore buttons are missing.