Weld hatching disappearing - IV2014 SP2

[graemev]

After making the drawing, including a section of the assembly, an modification was made to a weldment.  Upon updating the drawing, all weld cross hatching has disappeared.  Only the welds are affected, including those not changed during the modification.  Relaunching Inventor, and Rebuild All have no effect.  New sections also lack weld hatching.  Making a new drawing also has no effect, which leads me to believe the problem is inherent to the model.

Is there any way to recover the weld hatching?  Is there a particular problem with the workflow that has caused the welds to start behaving like surfaces instead of solids?