Concentric and Warp cause image's position shift before transition.

[AVAVT]

I forced the the slider's size to 800x600 during initialization:

window.myFlux = new flux.slider('#slider', {
autoplay: false,
captions: true,
controls: true,
width: 800,
height: 600
});

Each image in the slide has different size. For both Concentric and Warp transitions, the image's position is shifted before the animation start (usually about 50~100 pixels toward the top left but it varies)

[AVAVT]

Also, on Firefox (v23.0), Tiles3D and Blinds3D cause the image to scale up, becoming 2px wider and 2px higher (1px toward all 4 sides) before animation start.
The bug did not occur on webkit browsers.