Just deployed 1.29.0-wmf.7 to group1 wikis and seeing this error quite a bit
Fatal error: Access level to Wikibase\Repo\Diff\EntityContentDiffView::getRevisionHeader() must be public (as in class DifferenceEngine) or weaker in /srv/mediawiki/php-1.29.0-wmf.7/extensions/Wikidata/extensions/Wikibase/repo/includes/Diff/EntityContentDiffView.php on line 36