I had copied a few books to my phone to read with Moon+Reader Pro (same app I use on my tablet, where I do most of my reading), and was trying to use the sync-to-Google Drive feature to, well, sync them up. It's not syncing as it should, and I discovered that I have two different sync files in my GDrive, with variations on the filename. That probably explains the sync failure - the two devices are each looking for a slightly different sync file.
The most obvious difference is that with the tablet, I connect it to the computer via USB and with the phone, I've been using Calibre's content server. So tonight I tried connecting the phone by USB to copy books that way, but whenever I do that Calibre crashes once it notices that the phone is attached. I'm using 5.24.0 portable.
I ran in debug mode, and here are some lines that I hope will be useful: