Thanks for all the input and ideas on this issue. I contacted technical support and the representative I spoke with seemed to think that this is a bug. He tried the Geometry Pattern and spaced the instances 2.51 mm apart, so that they have just a little space between them. When he did so they worked fine, even though they do not work correctly when touching. He forwarded the issue on to R&D, so it will be interesting to hear their response.
In the mean time maybe one of the alternate techniques mentioned here will lead to a robust model. Then again, I might just beg a plead with management to let me model this part with SolidWorks. Some might say that SolidWorks creates patterns with dumb solids. After wrestling with Creo off and on for four weeks to create this part, those dumb solids are looking a whole lot like smart solids. 