Error message during upgrade - upgrade process aborted after this errormessage

Debug info: Duplicate entry '629-4. oplossing vraagstuk: Twee volkomen elastische kogelvormig' for key 'mdl_wikipage_subtituse_uix'
INSERT into mdl_wiki_pages (subwikiid, title, cachedcontent, timecreated, timemodified, userid, pageviews)
SELECT s.id, p.pagename, ?, p.created, p.lastmodified, p.userid, p.hits
FROM mdl_wiki_pages_old p
LEFT OUTER JOIN mdl_wiki_entries_old e ON e.id = p.wiki
LEFT OUTER JOIN mdl_wiki_subwikis s
ON s.wikiid = e.wikiid AND s.groupid = e.groupid AND s.userid = e.userid
WHERE p.version = (
SELECT max(po.version)
FROM mdl_wiki_pages_old po
WHERE p.pagename = po.pagename and
p.wiki = po.wiki
)
[array (
0 => '*reparse needed*',
)]
Stack trace:
line 394 of /lib/dml/moodle_database.php: dml_write_exception thrown
line 672 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()
line 187 of /mod/wiki/db/upgrade.php: call to mysqli_native_moodle_database->execute()
line 490 of /lib/upgradelib.php: call to xmldb_wiki_upgrade()
line 265 of /lib/upgradelib.php: call to upgrade_plugins_modules()
line 1352 of /lib/upgradelib.php: call to upgrade_plugins()
line 290 of /admin/index.php: call to upgrade_noncore()