Thank you for your post.
Our Development and Testing departments are already aware of this issue with the Data Viewer. There is also another thread on the Community that also discusses the issue so you can see what others have encountered:
I have attached your post to the original report. When more information becomes available, I will post again.
The thread is talking about only "Set Variable" script step, but it seems occur on many (all?) text box that allow entering calculation or literal text (like button bar label), when "invalid expression" is entered it is automatically quoted then become literal text calculation. (I think this is already aware of)