With TAC/OG Integration, the simplenews drafts folder at Newsletters->Drafts (/admin/content/newsletters/notsent) does not list correctly:

I seem to have resolved this problem by adding "DISTINCT" to the $action == 'notsent' $query in simplenews_admin_news(). This fixes the problem:

Creating patch for the fix and submitting it to Simplenews issues:
Documented internally here:
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