Bug: Scale keyboard shortcuts don't work correctly when one value is negative.
After Effects usually intelligently handles linked scale values when 1 value is negative and the other is positive (for e.g. -100, 100).
You can drag a parameter to proportionally scale the object. You can even type a value into one field, and the other will update accordingly (for e.g. changing 100 to 150, will make the other value -150).
However is you use the keyboard shortcuts, Ctrl + and Ctrl - (on the numpad), the values don't adjust correctly, and they cause the layer to become distorted.
Pressing Ctrl + should bring (-100, 100) to (-101, 101), but instead it brings it to (-99, 101).