Switching between the various views is a great way to check that the reader mattes are accurate. A great way to view the reader mattes as a covered overlay is to create solids on top of the footage and apply the roto to that layer. When a mistake happens, a roto artist will get notes or corrections from the supe or even directly from the client. Sometimes these are corrections for the delivered matte, or they might ask for clarification of a focus object. A consistent note a roto artist might get is that the matte has jitter. This phenomenon occurs when a point or set of points along a spline moves differently from the rest of the shape. The two surrounding points are staying the same relative distance from each other, but the jittering point is moving inconsistently between the surrounding points. The new key frame will be jitter free and correctly repositioned.