Problem with reseting vertex groups

I had hardly modified model of a char. Ofcourse vertex groups broke. I select all vertexes(A), press “remove from all”, and most groups has been reset, but few not(see pic)

I cant figure out why.

Im not sure why Remove from All Groups would miss some verts, after using select all.

In edit mode, if you set the mesh selection mode to Vertex select, then select one of the verts with the problem…
Then check the 3D view > Properties > Vertex Weights panel, it should show you which groups the vert is weighted to.

What you are showing is not a bunch of free flowing vertex. It has relationship lines between them (the dashed lines). Find out what they are.