Hi, hopefully this helps someone else.
I had the error communicating with device when transferring five books by a specific author to my kindle from calibre.
I tried so many things, resetting my computer, my kindle, deleting the books from calibre and reimporting them and reconverting them, changing leads, using different ports, etc. (Not necessarily in that order.)
Here is what worked for me - I changed the author name in the drop down menu, then they sent flawlessly.
OK, the author was first listed as Lionel Shriver, the correct name. This would not send to my kindle (nor could I save to disk).
So, I tried listing the author as Shriver, Lionel. This didn’t work, I think because it is just a variant of the original format.
I decided to try LION SHRIV - all five books sent flawlessly.
It’s not ideal, as the author is not precise, but it is enough for me to know who is in the file.
From my reading on this error, it seems it might be due to a faulty disk management system in my kindle, but, as I have other kindles, I am not too worried about this long term.