Does anyone else encounter this? If you have a movieclip that contains a motion tween which is split in the middle, copying the movieclip that contains it to another document may make the animation un-editable or even break it (as in some of the flash banners I'm producing).
It seems like all transformation points get shifted randomly and Flash somehow tries to "knit" them together again.
This also happen if you chose "save and compact" and may break your animation if it's more complicated.
I have recorded a video which shows this behaviour:
I also filed a bug report for that and hope it could be reconstructed. But seeing it in a video just illustrates the problem even better.
Unfortunately this (the copy nested split tweens across files) is a known issue. However, if you use copy frames instead of copy you shouldn't see this issue.
However, I haven't seen the save and compact problem even with the large complex files -- that shouldn't be touching anything to do with the spans. Are you able to reproduce this consistently or have some steps I can try?
I tried to reproduce what I thought I have seen when doing "save and compact", but it didn't appear again. Maybe the timeline was broken before I did that, so hopefully this is just a false alarm!