The node Math1034
is in two different subgraphs which isn't allowed. dot
actually emits the following warning:
Warning: MATH1034 was already in a rankset, deleted from cluster G
Warning: MATH1034 -> MATH2007: tail not inside tail cluster cluster0
Warning: MATH1034 -> n1: tail not inside tail cluster cluster0
The solution is to remove MATH1034 from the second cluster, and add the edge without constraining ranks:
{rank=same; n1[ltail=cluster0,dir=none ]; n1->n2->n3->n4->n5[dir=none];}
MATH1034 -> n1[constraint=false];