Particles Indexing not working...

So ive been using nDynamics for some debris being picked up and dumped by a mechanical claw. All good in the sense that it all falls exactly how I wanted it to. So I cached the particles.

But now when I scrub through it, after the first or second dump, the particles randomized indexing stops working, so that every bit of debris is the same piece (i have about 5 different sized/shaped rocks in the index) and they dont rotate...

I thought it might be something to do with changing the timeslider playback speed to 25fps instead of 'play every frame' in which i cached the particles in? Dont really know whats goin on, and dont want to cache the whole thing again if not necessary.

any help?

cheers,

- Josh