Unity -build for iOS using Xcode - broken animation

Hi, I would appreciate the forum assistance with a problem we are having: we are developing a mobile application which incorporates some animation in it. using Unity3d 4.5 and building with Xcode. recently we have encountered a "break" in the animation . (its a repetitive animation and the break happens at the same second each time). it happens only on the device (iOS) and not in the unity editor. I believe that it's a bug related to the build settings or xcode project/target settings since the same code can produce different outcomes (a version that used to work well will have broken animation in the next build).

any tips/comments/explanations would be much appreciated!

Meyrav