After defining a new backup folder on the same USB-Drive, the backup is working properly again. But it started a completely new backup. My conclusion so far: the appearance of the problem described in the summary has probably something to do with folder size, number of files in a folder, processor power or thereabout.
After defining a new backup folder on the same USB-Drive, the backup is working properly again. But it started a completely new backup. My conclusion so far: the appearance of the problem described in the summary has probably something to do with folder size, number of files in a folder, processor power or thereabout.