Exposed sorting: too many sort values added

screenshot attached

Or: how do I figure out which function calls a handler and when, so I can trace this sort handler call back?

Two more attachments.
- One shows two exposed sort filters. It will always add the default setting of the first exposed filter in the row.
- The other shows two non-exposed filters. The result is fine here.

views_handler_sort::query() also passes the default sort first when exposed. The difference is that when it passes the values to views_plugin_query_default::add_orderby() , the views_plugin_query_default::orderby property gets populated, it doesn't seem to be the same property?

When I check $this->orderby in the same page load, it populates orderby with the default value first, but the second sort value doesn't seem to be added to this array, instead it looks like a new empty array.

$this->orderby[] = array(
  'field' => $as,
  'direction' => strtoupper($order)
);