Mathematica Subgraph "Neat Example" not working properly in Mathematica 12

sg = Subgraph[g,
 Complement[VertexList[g],
   VertexList[NeighborhoodGraph[g, RandomSample[VertexList[g], 25], 1]]]];

The issue seems to be that Subgraph inherits the GraphLayout option value from the parent graph:

PropertyValue[sg, GraphLayout]

{"GridEmbedding", "Dimension" -> {25, 50}}

and, somehow, the vertex layout defaults to something weird when the number of vertices do not match the length of the coordinate list produced by the layout procedure.

So, you can

1. add the option GraphLayout -> Automatic (or use your desired setting):

SetProperty[sg, GraphLayout -> "SpringElectricalEmbedding"]

2. remove the GraphLayout property from g:

Subgraph[RemoveProperty[g, GraphLayout],
  Complement[VertexList[g],
    VertexList[NeighborhoodGraph[g, RandomSample[VertexList[g], 25], 1]]]]

3. use the option VertexCoordinates to retain vertex coordinates in g:

Subgraph[g,
 Complement[VertexList[g],
  VertexList[NeighborhoodGraph[g, RandomSample[VertexList[g], 25], 1]]], 
 VertexCoordinates -> {v_ :> PropertyValue[{g, v}, VertexCoordinates]}]

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