Yussef-
I think AE’s getting confused as to the amount of lights in your comp VS the shadow map resolution of your comp.
Hopefully this will quickly solve your problem-
go to Composition Settings (ctrl + k),
click to the Advanced tab,
and click on the Options button.
Boost up the Shadow Map Resolution from “Comp Size” to something more hearty (maybe 2000?).
This gives more resolution to the edges you’re shining the lights on.
If this doesn’t work, try changing your lighting setup a little.