Help: New JP6 – whining sound coming from mono-output jack

I just got my JP6 this Friday – which I am absolutely in love with – however, there’s a noticeable whining sound coming from the mono output jack. It’s silent enough not to be noticeable on most clean sounds but anything with distortion / compression on it will bring out this whine quite noticeably. Using the stereo-jack works fine.

Any ideas on what it could be? (I use a regular mono guitar cable into a Fractal Audio FM3; though the whine is also there when used straight into my interface and DAW and with different cables).

Not sure it’s a shielding issue since the position, direction or me touching metal or not has no influence on it. When I plug the cable into the mono jack I can hear a slight pop with the whining starting shortly after – so I assume it’s coming from the piezo-preamp / electronics? I never had this issue with any of my other guitars, and as mentioned the stereo-jack (used with a mono cable) works fine.

I just wanna make sure I am not missing anything before taking it back to my dealer to have it checked.