If I create a subclass of wxPanel via wxSmith->Add wxPanel it generates a 4 argument CTOR (3 defaults).  The new subclass compiles correctly.
If I then add this part by adding a wxPanel and setting Class name to my subclass name the object is newed with a 6 argument CTOR and fails.  wxPanel, of course,  provides a 6 argument CTOR (5 defaults).  I think my subclass CTOR should also be generated with 6 args (5 defaults).
This is very easy to work around since the CTOR is only written when the new class is created, not when it is later modified.  So I fix it once and it stays fixed.  But, unless I have misunderstood your intent, I am sure you want to correct it.
Paul