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ADUM4160 iCouplers EMI

Hello, during EMI/radio test (spurious radiated emission) we noticed non-conforming results regarding autorised radio emission level for our PCB design. We did carefull design. 43dBuV/m is the criteria for Spurious around 700 to 800 MHz that is the problem. We target medical device market. We are using ADUM4160BRIZ for usb safety and believe it may be the source. we need to reduce less than 5 dBuV/m. Note that In the area, we also have isolated I/O zone that we already improved for EMI reasons with ADUM226N0BRIZ and ADUM6028-3BRIZ (based on AN-0971 and Chris recommendation to replace a old design ADuM6404). Can you confirm that such spurious can come from by the ADUM4160 ? I had a look at the application note for icoupler products AN-1109, we we have Safety Stitching Capacitor 220pF but it seems we need to do more. What would be your recommendation ? I belive moving from 5V VDD1 to 3.3V and reducing data rate could be a good idea. Meeting isolation standard with other capacitor is not really possible beacause of safety standards. BR