Yep, it is a bug.

Do not know why, but for some properties, when you have changed them in the underlaying class from their default value, when you subclass that class, the property value is lost.

This is true for many ActiveX controls we have tried to subclass.
Have not found a fix, but found an workaround - in the Init method of the class we set all the "problematic" properties.

So, try setting the TitleBar property explicitly in the Init method. Do not forget DoDefault() in Init of your subclass/instance, if you have some other code added in it.