I've just managed to get Quality Check to blow up...
Spoiler:
No supported meta tag or non-xml cover in: The Story of Edgar Sawtelle / David Wroblewski
No supported meta tag or non-xml cover in: Century 01 - Fall of Giants / Ken Follett
No supported meta tag or non-xml cover in: Rizzoli & Isles 01 - The Surgeon / Tess Gerritsen
No supported meta tag or non-xml cover in: Rizzoli & Isles 04 - Body Double / Tess Gerritsen
No supported meta tag or non-xml cover in: Watchers / Dean Koontz
No supported meta tag or non-xml cover in: Inn BoonsBoro 01 - The Next Always / Nora Roberts
ERROR parsing book: \\Kez\e\Calibre Library\Elizabeth\John Sandford\Lucas Davenport 01 - Rules of Prey (41)\Lucas Davenport 01 - Rules of Prey - John Sandford.epub
Traceback (most recent call last):
File "calibre_plugins.quality_check.check_epub", line 709, in evaluate_book
File "calibre_plugins.quality_check.check_epub", line 1636, in _get_opf_tree
File "lxml.etree.pyx", line 2743, in lxml.etree.fromstring (src/lxml/lxml.etree.c:52665)
File "parser.pxi", line 1573, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:79932)
File "parser.pxi", line 1452, in lxml.etree._parseDoc (src/lxml/lxml.etree.c:78774)
File "parser.pxi", line 960, in lxml.etree._BaseParser._parseDoc (src/lxml/lxml.etree.c:75389)
File "parser.pxi", line 564, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:71739)
File "parser.pxi", line 645, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:72614)
File "parser.pxi", line 585, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:71955)
XMLSyntaxError: Input is not proper UTF-8, indicate encoding !
Bytes: 0x97 0x74 0x6F 0x20, line 14, column 298