Reference Plane Order

This is subtle. When you draw reference planes the order they were created plays a role in how a parameter will move them later. Draw two new vertical parallel reference planes, draw one on the left and then next to the right of the first. Add a dimensions and assign a label (parameter) to the dimensions. Flex the parameter value and watch the reference plane on the right move. If you have a lot of reference planes it can get confusing but this underlying behavior is lurking there.

You can force certain behavior by pinning reference planes, locking dimension or using the EQ constraint to force them to move equally about a center reference line. Like I wrote, it is subtle. Just keep it in mind while you do your family editing.