Kobo and Calibre
Have had similar problems where Calibre cannot transfer files to a Kobo Touch, though intermittent in my case, all mentioning the diskfreespace error It does seem the device is very sensitive to the USB cable used; my problems were worst when using the rather long and thin cable from a Kindle (just poor quality or some sort of sabotage?). Using a much shorter and thicker cable seemed to solve the problem for me. I also switched from a usb3 to usb2 port. Either should work in theory but real life sometimes doesn't know this! Suggest trying different cables and use a port connected directly to the motherboard rather than one of those diverted to the case front if you are using a desktop PC as these can also cause problems for some devices. Hope this helps.