I should have mentioned before that I also tried different USB cables and different USB ports in order to rule out those as a possible cause.
The eject device function in Calibre results in the same problem with the iMac complaining about a device not being ejected properly.
The results of my experimentation suggest that a factory reset isn't going to make any difference. With >12,000 books nicely sorted into collections and series over the past three years (thank you Project Gutenberg) it's not something I want to do on the off chance that it might help.
I think I'll try taking this issue to Kobo support, but as the normal way of adding books to a Micro SD card works with no problems, they may just send me back here or to Apple.
Thanks for your feedback.
I should have mentioned before that I also tried different USB cables and different USB ports in order to rule out those as a possible cause.
The eject device function in Calibre results in the same problem with the iMac complaining about a device not being ejected properly.
The results of my experimentation suggest that a factory reset isn't going to make any difference. With >12,000 books nicely sorted into collections and series over the past three years (thank you Project Gutenberg) it's not something I want to do on the off chance that it might help.
I think I'll try taking this issue to Kobo support, but as the normal way of adding books to a Micro SD card works with no problems, they may just send me back here or to Apple.
Thanks again for your feedback.