Comment #6 on issue 2589 by [email protected]: cyclic dependency when tempo, slur, and script present
http://code.google.com/p/lilypond/issues/detail?id=2589
I can't nail the bug down...it's exactly what you're saying. Sometimes it's there, sometimes it's not.
What is strange is that it comes through as a circular dependency, which are often easy to create flow charts for. Here, I get the sense that an Slur::outside_staff_callback, which is supposed to be for Scripts, is being accidentally chained to another type of grob (or a pointer to one grob suddenly points to another).
