New speaker cables - now audio seems panned right and left

How could I forget that,  it happened to me once not long ago,  I thought my system suddenly got more holographic..

Sounds like you purchased a set of cables from China. (just a supposition).

OFC cables historically take longer to break in.  What I would have recommended is a set of ribbon cables that use "OCC" solid core copper (with or without silver plate) Silver plating always tends to accentuate the upper frequency spectrum.

I have a very flat audio system response curve. I avoid plated cables and always go with "OCC" solid core copper. You will find that most of the harshness will be gone right out of the box. If you are careful in your search, you can probably find good speaker cables form CHINA fabricated from "solid core OCC copper". Beware however - - - sometimes the ads twist words around. Double check anything you buy. Personally, I have moved past CHINA for lower cost quality cables and have mine custom made for extremely low prices. All my cables are "OCC" copper. I have a wonderfully smooth sounding system, without spending a fortune.  VANDERSTEEN speakers should produce excellent quality sound and imaging, but the rest of your components need to be of equal quality. One weak link in the chain can kill the whole effort.

AXPERT

Now that's what you call a non sequitur...

Long time back, I noted same situation with Talon Chorus speaker. No matter which wires used, the sound can only be heard from within the box, but not outside. No imaging at all. It could also be a room issue or wired out of phase

How do the cables sound now that the phase issue is sorted? I'm considering trying some China cables to see how they perform in comparison