I’ve gone through everything. I even reinstalled a fresh uncustomized version of Vintage, deactivated over half the plugins, and I’m still getting that behavior.
Right now, the front page is one slider frame, and that funky set of sidebar widgets, only they aren’t attached to a sidebar.
There are no Inactive Widgets, and the widgets that are in the Primary Sidebar are not displaying.
Site running WP 4.8, Genesis 2.5.2
When I switch back to Genesis 2.4.2, both the fresh version & the custom version display the regular sidebar as expected.