in the file imagefull.php the following JText strings need to made javascript safe by setting jssafe value true
messages: {
selectimg: \''.JText::_('COM_JSN_IMAGE_ALERT_SELECTIMG'.'\',
uploading: \''.JText::_('COM_JSN_IMAGE_ALERT_UPLOADING').'\',
loading: \''.JText::_('COM_JSN_IMAGE_ALERT_LOADING').'\',
saving: \''.JText::_('COM_JSN_IMAGE_ALERT_SAVING').'\',
}
https://api.joomla.org/cms-3/classes/Joomla.CMS.Language.Text.html
Otherwise if the text string contains an apostrophe it breaks the javascript of the site.