Thanks for the thoughts, Jeff. They are posting in detail, but where the GL account key and dollar amount are the same on the lines for a single invoice the UDF values are coming through inaccurately. I've attached an example invoice where just under 50% of the UDF values made it properly into GL_DetailPosting.
Let it be known that there is a third-party add-on in the posting mix. They have DSD's multi-company for AP. I wouldn't think this would be the culprit, but maybe?