Apiman caching policy changes response format after first request

We have an api publiched in Apiman that works ok.

It is a REST service that returns a json via GET with one query parameter.

When I try to create a cached version of it, the caching policy behavior is not as we expected.

The first call to the cached api behaves ok After the first call, we expected that the apiman would return the cached response with the same format. But it is returning a xml with a cdata field containing the original response.