I just saw this on the logs:
IndexPager::buildQueryInfo (ProblemChangesPager) 10.64.32.115 1176 Key 'change_tag_rev_tag' doesn't exist in table 'change_tag' (10.64.32.115) SELECT /*! STRAIGHT_JOIN */ page_namespace,page_title,page_latest,fp_stable AS stable,fp_quality AS quality,fp_pending_since AS pending_since,fp_pending_since FROM `flaggedpages` FORCE INDEX (fp_pending_since),`revision`,`change_tag` FORCE INDEX (change_tag_rev_tag),`change_tag_def`,`page` WHERE (ctd_id = ct_tag_id) AND (fp_pending_since IS NOT NULL) AND (rev_page = fp_page_id) AND (rev_id > fp_stable) AND (ct_rev_id = rev_id) AND (page_id = fp_page_id) AND page_namespace IN ('0','4') GROUP BY fp_pending_since,fp_page_id ORDER BY fp_pending_since,fp_page_id LIMIT 51
Key 'change_tag_rev_tag' doesn't exist in table 'change_tag' (10.64.32.115)That key looks like the one that got removed while fixing change_tag table (T185355)
That index is also not present on tables.sql