Button widget returning to old position after SetPosition

When fiddling with a UI mod that repositions some buttons I noticed that a Button type widget goes back to a previous position when moused over.  I believe this is because (in widgets/button.lua:OnControl) clicking on the button saves its old position so that OnLoseFocus can restore it later.  But that old position isn't cleared and is set again after a mouseover.  Of course the game and almost no mods move buttons around so this doesn't show up much...

(A modder can workaround this by clearing o_pos before moving a button in code.)

I haven't done any DST modding yet but a brief glance looks like it probably does the same thing.