I had a simular problem.
Maybe the Scollbar have a bug.
It don't work if you put
panel1.AutoScro ll=false
and for example
panel1.Horizont alScroll.Value = 0.
In that case the problem is 0. Sometimes it don't work.
Try this too ...
panel1.AutoScro ll=true;
panel1.Horizont alScroll.Value = newValue; // Or VerticalScroll
panel1.Update() ;
panel1.AutoScro ll=false;

I hope...