GUI Designer. Make sure that "Generate GUI" setting has "Java source" value. Provide a custom component with custom property, e.g. of String type. Add this component to a form. In inspector provide non-default value of this property. Build. The code like is generated. Now go to custom component class and remove (comment out) custom property. In Designer everything looks fine, property is missed in inspector. Build project - you get the error in GUI auto-generated code. Set method is still there. It is not overwritten and causes errors. Probably custom classes should be realoded before compiling a form. Workaround: user can manually erase erroneous statement. Then compilation is Ok. Bug does not occur if "Generate GUI" = "Binary class files".