Click on "Questions" in the left menu of a course.
Create questions, including at least one of "Numerical" type.
On the "Questions" page, click on the "move" icon of a "Numerical" question.
You get a blank page.
With debug message enabled, I had a full trace (see attachment) that begins with line :
QuickForm Error: nonexistent html element Element 'multiplier' does not exist in HTML_QuickForm::getElement()
I could reproduce this on several servers with different browsers.