You could check the connections of the internal cables to the drivers of your speakers for looseness.
That was exactly my problem when I had an imaging issues. The image appeared to move about, sometimes in the centre where it should be, then moving to one side only, then back to centre again.
It turned out to be a slightly loose connection on a mid range driver. I have VMPS speakers which have three ribbon drivers for the mid range with a pair of external nuts on each one which holds the wires on the inside. These nuts had come slightly loose.
I'll definitely keep this in mind.
UPdate: I have been making big changes (mostly for fun) and for the learning experience. But in the process i have changed most all of the amplifiers in my system back to my very old Yamaha Integrated HT amplifier (running in stereo). I have also made source changes, but that is another story. At first I really missed the airy, detailed sound of the Optocoupler pre and my tripath chip amps. The solid state amps just sound different. But I value imaging so much that I was desperate.
Long story short once I took out my pre and amplifier my imaging has become rock solid and no longer do I question my sanity or my hearing. I should redo master set with the Yamaha now. Probably get even better results.
With a better tonearm and cartridge match (Technics and Denon DL103MC) music is so real and now I understand without a doubt what "effortless" means. So many words to describe audio you dont really know what audiophiles mean till you get a taste of it. I am watching the trading post ads for another amp/pre/intergrated I can afford. For now I am getting used to the Yamaha and am enjoying my music more than in a long time.
