Hi Steve, yes a Network has to be arranged in such a way that it forms a grid pattern, so that it can be essentially unwrapped to a 2D pattern. It's similar to how latitude and longitude lines on a globe can get unwrapped to a 2D flat map.
Could you post a 3DM file attachment with the curves that are acting strangely? That would let me take a look and describe what the problem is for your particular situation.
Here are some links to some previous discussions and examples of the kinds of layouts that won't work, maybe one of them applies to your example:
