One thing I'm confused about is that I thought Ketron keyboards were no longer being produced? But after doing a bit of searching, I realized that I was somehow mixing up Ketron and Technics in my head. (Sometimes things like that happen in my head!) If Ketron keyboards are still being produced, is there any sort of customer support department that your friend can contact?
By the way, I just remembered a similar issue that some people had trying to update their Yamaha keyboards. If I'm not mistaken, in that case the problem turned out to be the USB flash drive they were using, which for some reason wasn't fully compatible with the keyboards' operating systems. Your friend's problem might be similar to that, or it might be something completely different, but it might be worth looking into. Some manufacturers will post a list of USB flash drives on their site which they've tested with their keyboard models and have found to be compatible, so your friend might see if Ketron has published any similar sorts of lists. If they haven't, then his best bet might be to try using a USB flash drive that's older (as far as the USB version) as well as smaller (as far as the number of megabytes or gigabytes), because unless a keyboard is a brand new model built with the absolute latest and greatest electronic and computer components, it's usually going to be more compatible with older USB standards than newer USB standards.