RABAX_STATE error with Odata ?$format=JSON

Hello,

I get this error HTTP/500/E/Internal Server Error  RABAX_STATE

when i try calling my oData in format=JSON

here are a screenshot of the error i get

But when i tried with XML format in end its working !!

/sap/opu/odata/sap/ZDEMO_READ_IMAGE_SRV/EmployeeDataSet/?$format=XML

Is it a problem with the reimplementation of the methods

EPMPRODUCTSET_GET_ENTITY , EPMPRODUCTSET_GET_ENTITYSET

Or Authorization ?

Thanks