For just one of my content types -- the built-in Article content type -- the node option vertical tabs at the bottom of the add / edit form are not displaying correctly.
As shown in the attached screenshot, the first node option for whether to create a menu link for the node is displayed as a tab. All other node option fieldsets are displayed WITHIN the first vertical tab as collapsible fieldsets, not as additional tabs. This only happens for the Article content type.
I cannot figure out why this is happening. Clearly, some module is form_altering the node add / edit form, but I have no idea which one or why only for Article.