Shapes moving on their own: is this a bug or my own mistake?

Hi.

I'm having an issue with Storyline 2. I've created a menu using rectangles. Once the rectangles animate in, they sometimes snap into a different position to where they should be. I've tried to pinpoint the issue but haven't been able to. This problem is on scene 6 of the attached file. One more problem: the buttons I'm using to navigate my story look perfectly fine when I'm editing my slides, but the icons don't look properly aligned when shown in preview mode. Any help with either of these issues would be much appreciated.

Thanks very much in advance,

James