Anchor point problems with 'wiggle rotation' effect

I know I can use expressions insted of effects for wiggles, but in this case I'd rather just stick with the effect.

But when I rotate, it doesn't seem to correlate with the anchor point. It's as though the anchor point is in the top left corner.

See what happens when I add 'Wiggle Rotate' effect below... if I change the 'anchor point' properties in the effects window it doesnt appear to make any difference?

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