knob drag: mouse-up not always registered

Steps to Reproduce

	<slider mold="knob"
			minpos="0.0" maxpos="100.0"
			curpos="80" step="1" width="300px" angleArc="360"
			style="border: 1px solid black;" strokeWidth="20"/>

1) mouse down inside over the knob area
2) start dragging, the value follows the mouse movement as expected
3) drag over the value input area ( the value stops updating)
4) release the mouse button

Current Result

after releasing over the input field the the value still follows the mouse movement

Expected Result

follow the mouse when dragging over the input area
stop following the mouse then releasing the mouse button

Debug Info

a similar effect can happen when first selecting some text on the page, and start dragging the text over the knob-slider area, sometimes the slider keeps following the mouse movement after releasing the mouse button

Root Cause

Workaround