Portable Apps version of Scribus 1.5.8 takes very long to close

[Flaxx]

I'm using Scribus portable, as I'm using it at different places and not always on the same computer. This ensures that all internal paths are usable, almost. However, when closing the app, it takes really long before I can eject the USB-Stick and I have no Idea what Scribus is doing in the background as it happens even if the last file had been saved a while ago. And yes, Scribus is indicated as the blocking (busy) application.

Color profiles are saved within Scribus, Fonts within Scribus (that required every time to name the path within the settings) and PortableApps' font directory (that seems to work). All data are stored in an extra directory on the stick as well.

The Stick is a 64 GByte SanDisk USB3.0 and usually really fast.

Any ideas what can be the reason?