Katumba,
Making a Bug report about your issue is good advice, you will not only assist in improving the distro if indeed there is a bug, but also get the best diagnostic there is, and this will probably help you. Please give as much information as you can. In particular, provide details of your system (are you running 7.4?) tell us how you are trying to backup (I assume that what you call the web panel is in fact what we call Server-Manager, correct?), how is the backup utility configured (I assume you are using DAR and selecting backup to workstation?) , how is your USB device formatted. Thanks.