I don't fully understand it, but DPD does react to some chloramines given time. I can't really tell you more than that.

HOWEVER, that might not be your issue. If you don't rinse your sample tube out well AFTER each test, you can get similar, but bogus, results

Still, in your case, I think it's chloramines or CC, since you are smelling the chlorine. That will happen if you let your chlorine get low. I think the important question here is not the one you asked, but this one: "Why are chlorine levels in my pool so low?"

That's the question you need to answer.