Mp4 animation scattering

HI everyone,

I created a simple animation in which vector graphics interact with background pictures.

When I rendered it in mp4 I saw that in the resulting video graphics elements don't move smoothly: they scatter a lot and that's not the effect I was looking for. I would just like the graphics to follow the paths I drew (which they actually do when I watch the video in AE).

Any idea on how to solve the problem?

Thanks in advance