Copy and past is destroying my tweens

Hey out there;
I’m in the process of breaking up my 16000 frame movie into movieclips. I do the cut and paste into ‘create a new symbol’, ect. I’ve noticed something to add to my pain - some tweens drop out, instead of that nice straight arrow, I end up with dotted lines. Does anyone know why this is happening, and is there a work around?

If you start breaking apart the clips from the end of the whole movie, I think you can avoid this problem. I’ve noticed that flash doesnt like it when certain symbols are cut out of the timeline. Tweens often disappear when there is nothing to tween to.

thanks for the help, i’ll give it a shot