Incredible Disappearing Stencils
 

Greetings,

I have some imported Visio documents that appear to be periodically disappearing shapes. The shape is still there and selectable, but as a blank box with no contents. When it occurs, it appears to affect all instances of a particular shape. Re-opening the document or restarting Omnigraffle doesn't appear to fix the issue. Any idea what might be going on here?