Passenger speakers not fully working with AUX

Hi I'm new to this forum and I have just bought a Clio 09 dynamique S 1.5 dci. I have bought an AUX cable from eBay and turned the AUX setting on within the CD plate settings. Although I can hear music it's intermittent through the passenger speakers.

If anyone has any suggestions or who has had this problem themselves I would love to now how to sort it out. Thanks