Fields inconsistently revert to zero upon saving

[wxaggie11]

I don't know if this is a Visio bug or what, but I'll explain as best I can what is happening and hopefully someone has seen this problem before.

Lets say I have a shape with string shape data "PropA" inside of it, with a value of "cat". I click the text tool on the shape so that I can insert a field. So I go to Insert>Field>Shape Data>PropA. After clicking OK, "cat" appears in the shape. This is what I want it to do all the time.

However, when I save the drawing and come back to it the next day, the field inside that shape will have reverted to a zero. Furthermore, it doesn't do this for all the shapes. Sometimes it does it for a few but not all of them. And it's not just that particular shape that's causing the error.. All of them seem to be susceptible to this bug. And the very strange thing about it is when I go to insert the field again, the field is already set up to print PropA on the shape.

Has anyone seen this problem and knows how to fix it??