Interconect or Nait 3 issue

I have just bought a Nait 3 and CD 3.5, neither had a 5 pin interconect. I used a non Naim DIN 5 pin to RCA. DIN in CD and RCA in the phono input (no phono stage). Everything sounds fine, also used the same connection to check  the other inputs  i.e. RCA to source (TV)  DIN to other inputs, aux, cd, tuner etc. No problems every input works as expected.

Bought a "Naim" 5pin 180 degree interconect/Snaic, yellow code NA-46 off an auction site. When I plug this into inputs 2-CD and 3-Tuner I get a faint sound of the CD, like a TT into a non phono stage input.

When I plug into inputs 4-tape and 5-VCR their is no sound from that input, this is the bit I do not understand if I press any other input button the CD is playing at normal sound levels although sounds a little bit rough.

In the manual there is a diagram of the inputs. Inputs 2 and 3, the first pin is ch1 and the second pin is ch2 both input, third pin is -ve and forth and fifth nc. 

Inputs 4 and 5, the first pin is ch1 and the second pin is ch2 both input, third pin is -ve, the forth pin is ch2 and the fith pin is ch1 both outputs.

What I'd like some help and advice on is the "Naim" interconect the problem, could it be fake or is the amp at fault. Has anyone had a similar problem.