Sorry for my bad English

Uses an iPod touch 16 GB 4.gen (latest update) connected to the MDI input.
Do not have the possibility to use streaming
When I start Spotify and choose a song I get sound artist, song name and album name in the display.
So Far so good. But When I want to change to the next song on the steering wheel or on the VW RNS 510 Navigation display, it will not switch to the next song in the playlist in spotiy. However Jumped to a song stored on my iPod. The strange is that after listening two more songs I can press the down arrow on the wheel and the earlier songs can be selected. Anyone Can help me? Program Errors in the app or VW Navigation RNS 510 Some have mentioned at the the mdi cable must be replaced by a new one.
There must be more than me who have this problem
If someone solves this I become eternally grateful.