One great thing about Qt Quick is its lean&mean syntax. Implicitly derived sane values and consistency are one big factor behind the power of the language. In most cases nowadays it is recommended to transition existing transitions from main-thread bound Animations to smoother and more robust Animators. Unfortunately Animator implicit values don't work like expected and inconsistently compared to the older Animations. I have suspicion there are other inconsistencies as well, but at least Animator.to implicit value works differently to Animation.to.

import QtQuick 2.6

Rectangle {
    width: 100; height: 100
    Rectangle {
        color: "red"
        radius: width/2
        y: 30; x: 25; width: 30; height: 30

        // Works:
        /*SequentialAnimation on x {
            loops: Animation.Infinite
            NumberAnimation { to: 45 }
            NumberAnimation { to: 25 }
        }*/
        // Doesn't work:
        SequentialAnimation on x {
            loops: Animation.Infinite
            XAnimator { to: 45 }
            XAnimator { to: 25 }
        }
    }
}