SLIM framework always returning < before any return

I Have a problem, my slim response are always returning <, like this: <{
“code”: “401”,
“message”: “Wrong number of segments”

or this: <[{“denuncia”:{“id_denuncia”:8,

I think with a debugger you can find out where that is.
My guess: it’s in the frontend-controller of in the setup of your project (like the router or so)