Start by zeroing out your group transforms and layer transforms before pickwhipping anything. shape layers have their own logic and it's necessary to be meticulous in these things or you'll end up with a mess because groups within groups within groups can all have their own transform properties.
Thank you for responding. I'm confused what you mean by zeroing them out. Do you mean delete all keyframes? I am just confused as to why the child of a parent wouldn't automatically follow that parent's anchor point.
Scale and rotation are centered on anchor points. If the anchor point is on the left edge of one shape layer and on the right edge of another then they will scale in different directions when you tie only the scale properties with an expression. When tying shape properties together is is awfully easy to get the scale from Shape layer 1>Rectangle 1>Transform Rectangle 1>Scale tied to Shape layer 2>Transform Scale instead of Shape layer 2>Rectangle 2>Transform Rectangle 2>Scale.
A screenshot of your composition with the modified properties of the layers revealed will tell us and probably even you exactly what is going on. Just select the layer press the u key twice and then Print Screen and paste to the forum. If you are on a Mac you'll have to press Shift+Ctrl/Cmnd+3 and drag the screenshot from the desktop to the reply field on the forum.
You have anchor points all over the place and scaling is going to be centered on those anchor points.
What exactly are you trying to do? Explain that in detail and I can probably help you. This looks like an opportunity to use a group and scale the group rather than try to scale each individual element in the illustration.
I've learned from other forums that the child/parent relationship is different for individual shape properties, as in a child won't follow a parent's anchor point as it would when you affect the overall layer, it will always follow it's own anchor point. I've also learned that anchor points for individual shapes cannot be snapped to guides which is making everything increasingly difficult.
I essentially want to build and animate assets (utilizing parent/child relationships) while retaining a constant stroke width on everything. That's all I'm trying to achieve.
Did you ever complete your animation? Did the advice you received here help at all? Let us know if you still need help.