Hello,
Please check SAP note 2193693 - Limitations of the Design Studio Property Binding Feature.
Quote:
Accessing a bound property in scripting is not defined
Calling a get or set function for a bound property is not defined and will behave randomly.
Without considering conversion, does the getText() function actually work?
Another way to achieve what you want would be to use the getData() function on the datasource. Actually, Property Binding is only there to reduce this kind of scripting.
Best regards,
Tanguy