Hi all. What could cause the dimensions to lose there relations to the drawing?

I have created a part and then created a drawing off of it. Everything was looking good. Then I go back to the part and started to use some Surface Features to clean up some weird looking fillets that occured. And after I clean the model up and go back to the drawing, all my dimensions are missing there relations everything is that yellow is color (missing relation). So I go back to the model and in the feature tree I roll back to where I was before I started using the Surface Features and go back to the drawing and the dimensions have there relations again. What is causing this?

Thanks

Larry