Animation synchronisation in Three.js with Tween.js - animation

Question

I'm trying to animate sprites along a path in Three.js using Tween.js by chaining the animations in order to have something like this :
----#----#----#----#----#---- etc
Every sprite has its own tween animation, and I just delay each tween animation at the beginning. Each sprite has in fact N animations along the path (that is not a straight line) and I chain them to have a loop effect.
Everything goes well if the FPS is perfectly stable, but my problem is that if at some point I have a FPS drop, the animations of the different sprites are not in sync anymore, and the space between sprites is not equal anymore. I potentially end up with something like this :
---#--#----#-#-#-----#--- etc
I was wondering if there is a better approach for this, like having only one tween animation for all the sprites, but I don't know how to introduce the offset between each sprite on many line segments.
I cannot post the exact code has it is part of a bigger app, and won't be usable as is, but it looks like this :
// create animations
for each (sprite) {
for each (segment) {
var currentAnimation = new TWEEN.Tween(sprite.position).to({
x : segment.endpoint.x,
y : segment.endpoint.y,
z : segment.endpoint.z
}, animationTime).easing(TWEEN.Easing.Linear.None);
currentAnimation.delay(delayTime * currentSpriteNumber);
previousAnimation.chain(currentAnimation);
}
lastAnimation.chain(firstAnimation);
lastAnimation.onComplete(onEachSpriteAnimationCompleted);
}
// start the animations
for each (sprite) {
spriteFirstAnimation.start();
}
// to remove the delay when each sprite animation has made one loop,
// and instantly replace the sprite at the beginning of the path
// (my paths are not closed)
var onEachSpriteAnimationCompleted = function() {
sprite.position.set(starting position);
for each (sprite animation) {
animation.delay(0);
}
}