[OS X TeX] TeXShop 4.27: blank Preview window after typesetting

[Murray Eisenberg]

Sometimes now when I typeset a book-length document with TeXShop 4.27 under macOS 10.14.5, the Preview window just shows a dark gray and no content whatsoever! 

But the .pdf itself is OK: I can view in the Mac’s own Preview.app.

What could be wrong?
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Murray Eisenberg			murrayeisenberg at gmail.com
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