I don't know whether this applies to all circumstances, but I found a bug when trying to create a panning camera around an arrow in mid-air. I selected the frame from the replay of the arrow and set a time frame, then plotted a course around the arrow. but when I played the edit back, the arrow was not where it was when i set the time frame. I played it back multiple times and found that sometimes it was right and others it wasn't. Also, sometimes the arrow would not be visible during the playback. Finally, once I'd compromised with the positioning, the game crashed when I tried to rename it (however that bug has already been reported).
Just a suggestion, would it be possible to create a save or autosave feature to protect the edit in case of crashes or so you could pause and continue working on it later. if it already has these features and i just missed it then I apologise for my ignorance.