I downloaded the demonstration Dynamical Systems with Lorenz Attractors. Of course, I want to modify its notebook to help me understand the code and the math. However, even though the notebook now resides in my own directory, I'm unable to perform a "Save" -- only "Save as". Though I save it as DynamicalSystemsWithLorenzAttractors01 and 02 and 03 and ... I'm still unable to save the file like a normal .nb file. In addition, the NB file name in the NB window reads Dynamical Systems with Lorenz Attractors - Source, regardless of which of the NB files I open (01 or 02 or 03 ,,,) .

I've looked at the NB cells using Command-Shift-E to see if I could find notebook instructions controlling its behavior, without anything coming to my attention.

Could anyone explain to me how and why this notebook is behaving as it is?