digraph {
 concentrate=true;

 problem [ shape=record, label="<p1>p1|<p2>p2|<p3>p3" ]
 subgraph { rank=source; source }

 some   -> problem:p1
 source -> problem:p2
 source -> problem:p3
}

[erg] This is another old one, going back to 1.7 (July 2001). Since 1.7 doesn't accept anonymous subgraphs, one gets the same effect by adding an edge source->some. If the ports are removed, no trouble is reported but only one edge is drawn from source to problem.

digraph G {
 concentrate=true;
  a -> 4 -> b
  a -> b
  a -> b
}