See attached movie. And use standart HelloTableView application.

You can see, that during sorting per some columns knob in vertical scrollBar changes its size. That talks about some inconsistency in its size computing, because changing in lines order doesn't change their size and their count, so knob should stay of the same size. (This problem may be especially actual for little tables, when all content is not visible, and lines height is big, assuming that current algorithm thinks about lines count and not about their cumulative height)

Set minor priority a priori.