I doubt anyone has this. I'd seen it before but couldn't figure out how to duplicate it. Finally I figured it out on my PC/L4.6.
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Those ThreeHermits are busy, busy, busy messing up my library (in addition to refusing to delete themselves).
Actually I can reproduce this by first opening a library in a tab (I keep my library in a tab all the time). Then open the library into a tab or floating window. The ghost-books are actually there; just click on the missing title and no problem.
Don't think this is worth a bug report. But if anyone else runs into it, the buffering of the two open windows gets mixed up as the software writes one window while trying to close the other.