9428535 created the issue

When dragging file(s) to a folder of a previously disconnected SFTP server, the file(s) appear(s) to be uploaded (transfer window shows progress, updated content on server), but afterwards the GUI is unresponsive and the app needs to be killed.

Similar symptoms can also be observed when the server connection is lost (that is not disconnected by user via GUI but e.g. WLAN network connection problems).