I noticed a similar problem with image when I first started getting into high end audio 20 years ago. I tried many things until I noticed the problem occured on all systems, including those in dealer showrooms. I tried moving the speaker to compensate for the offset image, but something about that approach does not seem right.
To make a long story short, I finally concluded that I have a slight hearing loss in my right ear. I can adjust the balance control to about 2 o'clock and the image centers fine. I did a fair amount of hunting in my younger days, and suspect this may have contributed to the loss in my right ear.
I am convinced that others people have a similar problem and do not know it. A high end system is so resolving that small losses are noticeable. Whenever someone comes to hear my system, I frequently start by playing something with a good center image (female vocal) and ask them to point to the singer. It does not happen often, but I have had people point to one side or the other. So I adjust the balance for them so they can hear what a true image sounds like.
Good luck.
