I have been down this road where I thought imaging shift was a result issues like the room, the electronics or my ears, but symmetric speaker placement along the center line of the room, mirrored toe-in and equal distance of the speakers to the listener (basically speaking) will fix it.
Diagonal seating?
Our room is configured such that the listening position has to be on a diagonal in relationship to the speakers. I try to turn my head so my ears are square to the speakers, but often I am listening while I’m doing something that needs my attention centered. It’s difficult for me to ascertain how much this affects the sound. I have noticed the soundstage is uneven unless I do something to compensate. I don’t know whether this is because of variable hearing from one ear to other since I am now 70 years old or it has something to do with the diagonal configuration.
Any thoughts?