Vahraz

Hi all, I am trying to add different video clips (portraits) into a frame (this is for a choir singing exercise), but when I put some of the clips side by side, the common side of the two clips goes black. This is not due to the black background i.e. when I add a white background, the black side effect still exist. This should be happening because of a kind of shadow effect I guess. Anybody know how to get rid of this? Thanks Guys 🙏