Moving multiple clips horizontally is handled wrong by undo. If you undo your move, it visually looks correct as the clips in the timeline jump back to where they were before. But if you try to playback it, you will notice, that under the hood, they are still where they were before the undo. If I now save and close the project and open it again, the clips are where they were before the undo.

I also quickly recoreded a video where you can see what I mean:
https://goo.gl/photos/gdMQJnYo4kae9vf89

I'm using Kdenlive 16.08.2