design binder closes

When I have an assembly open, and using Design Binder (for me, this is a .doc file open in Word), I often make notes in the Design Binder about what updates are still needed, and what next steps in a project are.

However, if I open a part from the assembly, the Design Binder closes and does NOT save my updates. Is there a way to prevent this? Have I found a bug in the software?

SolidworksModeling And Assemblies