Potential Textbox Bug?

I’m not sure if this is a bug or my own misunderstanding of the software.

The text is perfectly editable within my project until I set the size of the text box. After this I am unable to edit the text after running and this is irreversible, even if I change the textbox size back to (None, None).

If anyone has experienced this or knows a solution, I’d appreciate any help.

cheers,
Adam