i looked at how gsm jammer works (and jammers in general) : they pollute the DL signal, not the UL.
So if you see UL noise in your qos, it means it is probably another device. The best step now is to go around the area with your frequency scanner, measuring the UL band power. You will quickly localize the interferer.
Why is it localised in your band only ? I don’t know. How did you measure that ?