XML Projection when edit and resend- why not available to edit XML- custom classes

I'm not sure why on some message you cannot edit/resend and change the inforatmation in the message 

i.e. 

Property property1As Messages.MesaageType1;

Property property2 As Messages.MesaageType2;

Property property3 As list Of Messages.MesaageType3;

All extend  Extends (Ens.Request, %XML.Adaptor)

is there anything we are missing?