It's a shot in the dark, but maybe worth it.
I would try using 3D animation on iOS as it uses hardware acceleration:
-webkit-transform: translate3d(X,Y,Z);
See here for more information: ' 3D Conversion Functions '
There may also be some problems with very large images on iOS. Maybe this is the best solution to cut them into pieces. Learn more about this: "Know iOS resource limits. "
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