(The latest deployment of DiscussionTools permalinks backend to group1 wikis T315353#8392662 has resulted in some new errors, although a lot less numerous this time. It really is a gift that keeps on giving.)
There are a few occurrences of "Duplicate entry '0-XXX' for key 'itr_itemid_id_revision_id'" (where "0" is in fact always 0, and "XXX" is different revision IDs).
This looks like a bug in our code – that value should not be zero.
(This is distinct from T323080: "Duplicate entry 'XXX-YYY' for key 'itr_itemid_id_revision_id'" in "INSERT INTO `discussiontools_item_revisions`")