Put a break-point in the set method of the attribute and then select the value in drop down in UI and check if debugger is stopping there or not.
If its not being called then put the below code at end of Get_attr_name method...
CURRENT->SET_PROPERTY(
IV_ATTR_NAME = 'attr_name' "#EC NOTEXT
IV_VALUE = Value).
Or if debugger stops at set method then debug it and check if the value is set in the entity or not..