Response Transformer - Plugin Not Work For Me

I am trying to use Response Transformer plugin to transform response before sending its to caller.
Unfortunately it is not working for me , what I am trying here is to add a Header and a Json Field win response.

After trying all option I realized that the response content length play some role here because I am able to perform above things with response having lesser contents.

Can any one clarify whether there is any relation ship of content length here ? As will smaller response I am able to do Transformation but not for medium size ones.

Example -
Smaller Size where things works -
{“firstName”: “my-first”, lastName: “last-name”}
Response where transformation did not work for me -
{“id”:’'", “org-id”:’'", “origin”:"", “city”:“", “Country”:***”,
“Date-Of-Birth”:“",“School”:"", “company”:"",“id-card”:"******”,

Any pointer here will be highly appreciative.