Recently had the same issue, for some reason some values duplicated in database: in my case i found duplcites in several, but for example one to mention: elementor_template_type
post_id 22 26 28 30 count 2 2 2 2
so post ID 22, had two lines of the same, made backup of DB and tried deleting one duplicate, then all was solved. could be any meta value in your case or multiple metas duplicated