The other day, I hit the "restart Calibre in debug mode" twice. The first time it just closed. The second time it appeared to close, but I saw it was minimized in the doc. I don't know if it was in debug mode or not, I didn't notice it running any differently.
Today, I have hit that button 5 times in a row, which closed the application 5 times. (and then I opened it manually).
So I haven't figured out how to use debug mode.
So I tried updating Calibre, as I noticed a recent update (as normal). I got locked file errors, and don't know enough to fix them. I logged in as Administrator, and tried updating. Same problem. So I renamed Calibre.app to CalibreX.app, and installed Calibre from scratch, then rebooted to my personal (non-administrator) account. That fixed the problem, I loaded the book
. I'll delete CalibreX soon.