If you are running the Mac App Store version of NeoOffice on macOS Sierra or High Sierra, you will find that opening PDF files or installing most extensions will fail. This is due to Apple's recent security updates to macOS Sierra and High Sierra which breaks NeoOffice's PDF and extension loading code. If you are running the Mac App Store version of NeoOffice on macOS Sierra or High Sierra, you will find that opening PDF files or installing most extensions will fail. This is due to Apple's recent security updates to macOS Sierra and High Sierra which breaks NeoOffice's PDF and extension loading code. AssertionError: assert($y < $this->seq[$k]) in /html/neowiki_root/includes/DifferenceEngine.php:951 Stack trace: #0 /html/neowiki_root/includes/DifferenceEngine.php(951): assert(false, 'assert($y < $th...') #1 /html/neowiki_root/includes/DifferenceEngine.php(1047): _DiffEngine->_diag(1, 5, 1, 9, 5) #2 /html/neowiki_root/includes/DifferenceEngine.php(831): _DiffEngine->_compareseq(1, 5, 1, 9) #3 /html/neowiki_root/includes/DifferenceEngine.php(1212): _DiffEngine->diff(Array, Array) #4 /html/neowiki_root/includes/DifferenceEngine.php(1371): Diff->__construct(Array, Array) #5 /html/neowiki_root/includes/DifferenceEngine.php(1639): MappedDiff->__construct(Array, Array, Array, Array) #6 /html/neowiki_root/includes/DifferenceEngine.php(1784): WordLevelDiff->__construct(Array, Array) #7 /html/neowiki_root/includes/DifferenceEngine.php(1497): TableDiffFormatter->_changed(Array, Array) #8 /html/neowiki_root/includes/DifferenceEngine.php(1449): DiffFormatter->_block(119, 5, 119, 5, Array) #9 /html/neowiki_root/includes/DifferenceEngine.php(434): DiffFormatter->format(Object(Diff)) #10 /html/neowiki_root/includes/DifferenceEngine.php(346): DifferenceEngine->generateDiffBody('__TOC__\n\nNeoOff...', '__TOC__\n\nNeoOff...') #11 /html/neowiki_root/includes/DifferenceEngine.php(302): DifferenceEngine->getDiffBody() #12 /html/neowiki_root/includes/DifferenceEngine.php(286): DifferenceEngine->getDiff('showDiff('showDiffPage(false) #15 /html/neowiki_root/includes/Wiki.php(378): Article->view() #16 /html/neowiki_root/includes/Wiki.php(48): MediaWiki->performAction(Object(OutputPage), Object(Article), Object(Title), Object(User), Object(WebRequest)) #17 /html/neowiki_root/index.php(99): MediaWiki->initialize(Object(Title), Object(OutputPage), Object(User), Object(WebRequest)) #18 {main}