Sorry this can still fail. It looks like callback for each thread has to be different.......

suggested work around is to clone image before locking and animating it - this removed possibility of deadlock. This should make all animations thread safe I assume!

e.g.

 public class CustomPictureBox : RadPictureBox
    {
        protected override RadPictureBoxElement CreateImageEditorElement()
        {
            return new CustomRadPictureBoxElement();
        }
    }

    public class CustomRadPictureBoxElement : RadPictureBoxElement
    {
        public override Image Image { get => GetPaintImage(); set => base.Image = value; }

        private Image GetPaintImage()
        {
            Image image = base.Image;
            if (image == null)
            {
                return null;
            }
            Image paintImage = image;

            Image aniimage = (Image)image.Clone();      //<1mS
            lock (aniimage)
            {
                this.AnimateImage(aniimage, false);     //< 1ms
                ImageAnimator.UpdateFrames();           //23mS for test GIF

                paintImage = image;
                return paintImage;
            }
        }
        private void OnFrameChanged(object o, EventArgs e)
        {
            this.Invalidate();
        }
    }