Anchor at 0.5 causes glitchy rotation

[youyise]

I'm trying to rotate a simple box, which works fine. But as soon as I set both its anchors to 0.5, it starts to "teleport" at certain angles. Like this:

(watch what happens when it reaches 0)
Box(#CENTER, #CENTER, RectSize, RectSize/2, #WHITE, {rotate=CurrAngle,AnchorX=0.5,AnchorY=0.5})

Under certain circumstances it also glitches at 45, 90, 135 etc angles.
Full code here (sorry I messed up the formating of both hws files, please ignore my stylistic blunders).

[airsoftsoftwair]

Confirmed. I'll fix this.