Edges not moving with object

lexbaird

I'm rigging a model in DS 4.8, and have created face groups with the Geometry Editor, assigned faces, assigned bones to the faces, and used the weight map brush option to "fill by bone selection groups". This has worked on 95% of my model, but there are a few face selection groups that when adjusted with the assigned parameter dial, leave behind some edges. They don't move with the rest of the object group. (see picture). As you can see, the weight map is 100% red. What can I do to add these stationary edges to the transform movement, so the object doesn't distort?