Attached application has infinite loops and when it is on the last frame of the animation, it seems to start the next run and reads the current 'from' value from the item and starts another loop from that value of the last frame to the actual end. This causes it to slow down more and more until it eventually gets to from==to and stops.

It probably doesn't make any sense have loops > 1 without setting 'from', but I don't think the behavior with the last frame of the animation should slow down.

At least some error/warning could be printed that this doesn't make sense, and/or just have the same behavior as loops==1.

import QtQuick 2.12
import QtQuick.Window 2.12

Window {
    visible: true
    width: 640
    height: 480

    NumberAnimation {
//        from: 90
        to: from+360
//        loops: Animation.Infinite
        target: rect
        properties: "rotation"
        running: true
        duration: 1000
    }

    Rectangle {
        id: rect
        width: 300
        height: 10
        color: "red"
        anchors.centerIn: parent
        transformOrigin: Item.Center
        onRotationChanged: console.log("rotation changed to", rotation)
    }
}