Why doesn't this CSS animation work in IE10?

Question

This JSFiddle contains a CSS animation that works for me in Chrome, Firefox and Safari, but not IE 10. I know IE 10 doesn't need the -ms- prefix, so that can't be it. I can't see anything wrong with this:

@keyframes snapVertical {
  0% { background-position: 0 0; }
  16% { background-position: 0 0; }
  21% { background-position: 0 -136px; }
  37% { background-position: 0 -136px; }
  42% { background-position: 0 -272px; }
  58% { background-position: 0 -272px; }
  63% { background-position: 0 -136px; }
  79% { background-position: 0 -136px; }
  84% { background-position: 0 0; }
  100% { background-position: 0 0; }
}
.animation-snap-vertical {
  animation: snapVertical 4s cubic-bezier(0.165, 0.840, 0.440, 1.000) 0s infinite;
}

Why doesn't this work in IE 10?

EDIT

Why does the horizontal one work, but not the vertical ( fiddle )?

Horizontal animation:

@keyframes snapHorizontal {
  0% { background-position: 0 0; }
  16% { background-position: 0 0; }
  21% { background-position: -176px 0; }
  37% { background-position: -176px 0; }
  42% { background-position: -352px 0; }
  58% { background-position: -352px 0; }
  63% { background-position: -176px 0; }
  79% { background-position: -176px 0;}
  84% { background-position: 0 0; }
  100% { background-position: 0 0; }
}
.animation-snap-horizontal {
  animation: snapHorizontal 4s cubic-bezier(0.165, 0.840, 0.440, 1.000) 0s infinite;
}

Answer 1

It looks like a bug in IE (see similar SO question ). To get around this, I simply changed the initial and final offsets to 0.1px instead of 0. This seems to have solved the problem. The solution code ( jsfiddle ):

@keyframes snapVertical {
  0% { background-position: 0 0.1px; }
  16% { background-position: 0 0.1px; }
  21% { background-position: 0 -136px; }
  37% { background-position: 0 -136px; }
  42% { background-position: 0 -272px; }
  58% { background-position: 0 -272px; }
  63% { background-position: 0 -136px; }
  79% { background-position: 0 -136px; }
  84% { background-position: 0 0.1px; }
  100% { background-position: 0 0.1px; }
}
.animation-snap-vertical {
  animation: snapVertical 4s cubic-bezier(0.165, 0.840, 0.440, 1.000) 0s infinite;
}