Adding keyframe animation messed up timeline order
 

I added a simple animated PNG at the start of an FCP project I started a couple of weeks ago. It looked great but when the animation has spun off the screen the clips played are not the ones which are next in the timeline and are appearing out of sequence and earlier than they should.

Is this because I didn't think of adding the animation until later - I mean, should animated sequences be done at the time you are editing everything else at that point and not something you should go back and do later on???