yep, thats what i found out too, it must have to do with the engine running in window mode, with objects moving at higher speed when a static camera is looking at them. i think it's not been noticed yet, because a lot of people develop in fullscreen or use a moving camera, not so high speed and so on...
maybe its a rendering issue? but i doubt that because the behaviour seems to change when you mess with the fps_ or time_smooth variables, but you cant get rid of it.

i just created a bug report regarding this over in the bug reports forum. maybe this will reveal the cause of this strange behaviour.