Arrow animation from down to up not animating

[Mvdl]

Hi. I found out that the arrow in the header is not animating on both states; from up to down and from down to up. If the cells are growing, the arrow animates nicely 90 degrees clockwise from up to down, but the other way around it just 'jumps' without animation. You can make this easy visible by slowing the animation down to a second or 3.
Is this intended behavior? Is there a way to make the animation back up also smooth?

[Mvdl]

Never mind, I also found out that an animation duration of 0.25 seconds or more causes this issue. 0.2 seconds is probably just fast enough before the HeaderView gets (re)initialized and so the full animation will be visible.