It turns out I had overwritten the widget($args) within the widget, hence the before_widget got echoed but not the after_widget.
I renamed the widget($args) variable, and all references to it, then the plugins functioned as expected.
It turns out I had overwritten the widget($args) within the widget, hence the before_widget got echoed but not the after_widget.
I renamed the widget($args) variable, and all references to it, then the plugins functioned as expected.