Using two posts_orderby add_filter makes conflict

In the database definition of WP, in the table that links posts to terms, there is a term_order field. But this term_order is the order in which the terms are assigned to the post, NOT the order in which posts are assigned to a term.

You can see the intent behind the term_order field in this WordPress core ticket:
https://core.trac.wordpress.org/ticket/5857

Instead, modify the output of WP_Query with a taxonomy query, and order by date.