Hi @gtso86
Could you please tell me how did you add the thumbnail? It seems I can’t do it in my installation.
I believe you can fix it by using a custom CSS code. You can use the “acf/input/admin_head” hook to add the custom CSS code. This page should give you more idea about it: http://www.advancedcustomfields.com/resources/acfinputadmin_head/.
I hope this helps.
