Another factor that produces an over speed is when a short cut is entered on lnav during a vnav descent.
The logic commands an energy saving speed reduction,with a drag required message. the speed barkes are insufficient to provide a slow down and a wallow back to the new path so the aircraft noses over to regain the path, having just nosed up to slow down.(go figure) It happens quickly and is obviously exacerbated by winds and altitude.
I tend to slect lvl change whilst the pnf enters the shortcut and then tidy it up back into vnav.or a combination of previous tips ad the above.
Ps most dramatic effect on descent point is achieved by adjusting the programmed tail/head wind at a lower alt.i.e 10000' due to the proximity of the 250 k limit and the need to get the speed off earlier or later as the case may be, before pasing 10000'. This is the only point the aircraft seems to know it cant get down and slow down so it kicks the arse out of it and descends much earlier.
Jungle rules no science.
your bird major