json encoding issue

[jns2011]

I have successfully used this framework on several projects. However I am experiencing an issue that is driving me crazy.
I do the following:

Lets say I have a PHP class already defined with a GET implementation (properly working).
Then I create a new PHP class on a new file and paste the previous code on it.
I rename the class with a new name... and set the new route. So .. at this point I have a new route defined with the very same functionality. The problem by invoking this new route is that json encoding stop working for this new particular script while the original script still works fine.
Any help about why is this happening is appreciated. Thanks