Plot scale not saved to layout?

This is a model space printing question -- I don't use paperspace at all.

My settings have "Save changes to layout" checked under Program Options > Plot and Publish.  When I print something, I choose the option "Use plot settings from" -- Layout in the drop-down box at the top of the plot dialog box.

After plotting and saving the drawing, if I re-open the drawing and plot again, all the settings are there from the last time except the plot scale is not set to anything -- it is "null" and I get an error message if I try to plot without re-selecting a plot scale.

Is this a bug, or am I missing something?

Thanks.