Questions and discussion for this lecture live here. Fire away by hitting Reply below 
When the force property is updated the reset of the analysis should take place.
However this does not happen when the 
or 
buttons (on the side) are used.
It appears that removing/adding data this way is not seen as an update of the force_prop_group.
Yes - this would be a sensible modification to make since we never really want results stored that are out of sync with the state of the structure, as defined in the side panel.
S