The issue is present in betalabs too.
On a SD board click to sort topics - the Console will display
Uncaught TypeError: Cannot read property 'css' of undefined at OoUiMenuSelectWidget.OO.ui.mixin.FloatableElement.computePosition at OoUiMenuSelectWidget.OO.ui.mixin.ClippableElement.getHorizontalAnchorEdge at OoUiMenuSelectWidget.OO.ui.mixin.ClippableElement.clip
Note: If Dev tools panel is opened at the bottom of the page and a SD board is clicked, then moving the dividing line will cause numerous errors such as above.