Arreglar errores en algunas páginas de artículos en Joomla!

Tengo instalada la última versión de Joomla! 3 y hay algunos artículos (pocos) que dan error y no sé cuáles son los motivos. El portal tiene muchos contenidos y sólo algunos dan ese error que reproduzco a continuación:

Error

RuntimeException: Error decoding JSON data: Syntax error in /var/www/vhosts/[login to view URL]:78 Stack trace: #0 /var/www/vhosts/[login to view URL](374): Joomla\Registry\Format\Json->stringToObject() #1 /var/www/vhosts/[login to view URL](76): Joomla\Registry\Registry->loadString() #2 /var/www/vhosts/[login to view URL](170): Joomla\Registry\Registry->__construct() #3 /var/www/vhosts/[login to view URL](425): ContentModelArticle->getItem() #4 /var/www/vhosts/[login to view URL](42): Joomla\CMS\MVC\View\HtmlView->get() #5 /var/www/vhosts/[login to view URL](102): ContentViewArticle->display() #6 /var/www/vhosts/[login to view URL](655): Joomla\CMS\Cache\Controller\ViewController->get() #7 /var/www/vhosts/[login to view URL](118): Joomla\CMS\MVC\Controller\BaseController->display() #8 /var/www/vhosts/[login to view URL](702): ContentController->display() #9 /var/www/vhosts/[login to view URL](43): Joomla\CMS\MVC\Controller\BaseController->execute() #10 /var/www/vhosts/[login to view URL](402): require_once('/var/www/vhosts...') #11 /var/www/vhosts/[login to view URL](377): Joomla\CMS\Component\ComponentHelper::executeComponent() #12 /var/www/vhosts/[login to view URL](194): Joomla\CMS\Component\ComponentHelper::renderComponent() #13 /var/www/vhosts/[login to view URL](233): Joomla\CMS\Application\SiteApplication->dispatch() #14 /var/www/vhosts/[login to view URL](225): Joomla\CMS\Application\SiteApplication->doExecute() #15 /var/www/vhosts/[login to view URL](49): Joomla\CMS\Application\CMSApplication->execute() #16 {main}

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Project ID: #33120077

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