I don't know if this is a bug or what this is, but I have custom text fields inside a grouped master that keep disappearing upon saving. What I mean by disappearing is that the value goes to zero and seems to not understand the custom formula I entered upon saving. I have a shape data cell (inside the whole grouped master) called Prop.Title that I want displayed in a text box, so I use Insert > Field... > Custom Formula and enter into the text box:
=Sheet.1!Prop.Title
(of course this is only assuming the shape has ID 1, which I can never be sure. There must be a better way to do this but I will continue)
When the code is entered into the Custom Formula field the data shows up. When I save the document, the title inside the text field reverts to zero.
WHY? >:(
The behavior that you describe is unusual, not expected. Visio should retain the shape data and will automatically update the shape ID as needed. I could not replicate your situation, but am enclosing a Visio file to show what I tried.
The Visio file has two additional groupped shapes. The 2nd one was just a copy of the 1st to show that Visio will update the sheetXX reference. The 3rd was a result of copying the 1st shape and placing it on a stencil, and then dragging the shape from the stencil and placing it on the drawing. Again, no unusual behavior. This final version was saved, closed, and re-opened. Still OK. Visio then was shut down and restarted. Still OK.
HTH
Wapperdude