PSTN design

We have a PSTN design that is failing one test for China NAL testing. It passes in all other countries. The only failure is Return Loss at 2km, and it is failing by 0.5 dB We use the Silicon labs Si3050 and Si3019 chips and their standard reference design for their DAA We are looking for someone who direct experience using these ICs and the SiLabs reference DAA and passing China NAL.