The bug:
The Static option should behave like other drop down lists - see the print screen

Details:
There's a check box, next to it a label "Static", and a drop down arrow.
Clicking the Static label results in checking/unchecking the check box. In stead, it should make the drop down list to come down - like in case of Layers or Resolution settings, and only clicking on check box should check/uncheck it.

Moreover, it is quite easy to miss-click on the tiny drop down arrow and click on the 'Static' instead - this would again check/uncheck the box and cause all the earlier selections on the drop down list to be lost.

Finally, it is laboursome to select items from the dd list, as it keep disappearing every time an item is selected. Let it stay visible, until user makes all his selections and then clicks away.