You're not alone. I have the same problem. I'm not entirely invested in trying to fix because I'd like to get Android Auto at some point. But if someone out there knows the solution doesn't involve taking the unit out, please help us.
mine just went to shit yesterday. 2013 gti with the RNS-315. will connect to my phone for about 10 seconds and play music and then disconnect my phone. cant listen to music or do anything and its driving me nuts that I might have to use the aux. looked everywhere but cannot find any solution :/ let me know if yall find anything