Great Naim sounds are back! But need help understanding some things and find a possible solution.

In my efforts to make my Naim system sound the way it should I've tried serveral, sometimes radical things, all with small incremental improvements.
It wasn't until this easter I finaly got it sounding right (understated) again. The difference was realy quite shocking.

 What I was experiencing is best described as a certain intermittent ringing, tiring digital distorted sound quality at some vocals which to me were unbarable and directly noticable but very difficult to reproduce. This all started to happen after installing a Supernait mk1 recently.

 The rest of the system consists of: CD5i2 on CD input (din) Pro-Ject turntable with Stageline N with I-Supply on tuner input (din) Setop Box on Coax digital in (AV) TV screen on optical digital in (Aux) All on a dedicated, propperly grounded spur.

Latest changes were testing a pair of 5m long cables of similar layout as NacA5 instead of my 2,8m pair NacA5 and disconnecting everything from the spur except the Snait and CD5i2.

I also had my Nait5i2 back in place to doublecheck what I was hearing, but everything sounded just fine this way, so back in its box it went. I have tried the NacA5 cabling again, and while it did sound different, I prefered the longer lengths.

What I did notice by accident when I made the mistake plugging the CD player over from the Nait to the Tuner input of the Snait was a certain level of crosstalk in one chanel from the tuner input to the cd input and vice versa (Chanels swapped) The same happens with the Tape input. Under normal conditions, I have an I-supply powered stageline N connected to the tuner input.

The Crosstalk was alarmingly clear and as soon as the phono stuff is connected the sound degrades. this had led me to believe I have found the problem.

1. Is a clear level Crosstalk to be expected when using two inputs close together with the amp at about 8:30, 9:00? admittedly, this is quite loud with line level sources. (The Nait 5i2 has nothing of sorts)
2. Could a mechaical resonance somewhere in the phono chain cause the amplifier to oscillate and distort trough the CD input?
3. Could this issue be adressed by removing the I-Supply and 4-5 interconect use a (yet to be bought) Snaic5 to connect the Stageline to Aux2 input?

Another option is to have the Supernait checked for a defective relay, which possibly makes the crosstalk worse. Though I can hear swithing when toggling trough inputs.

Very interested in your toughts/experiences.