Probably not what you want to hear, but I gave up in the end - VERY expensive for a sh1t sound. The RCD is quite possibly THE worst Head Unit on the market
I've resorted to a Griffin FM adaptor, as it didn't make ANY difference to the woeful sound of the RCD.
Advice?
Bin the RCD? Go aftermarket. Even the RNS might be OEM, but it still isn't very good (all imho, of course!)
If you want proper functionality, go aftermarket.
The other options to you are -
Dension ICE Link
Parrot ik9200
There are two of the top of my head, BUT they won't get around blue-screened box of sh1te in the dash!!! LOL!!
Good luck either way
Dan