I did purchase these used, although this is not a new issue. It's been a "feature" of the right speaker for as long as I had them, I think. I'm just finally digging in to addressing it.
At first when I purchased them, I set them up in my room and listened for a while, not taking any measurements (because they sounded so good and I was just enjoying the music). This was also before adding any treatments to my room.
I did always feel like the image pulled a bit to the left, but had figured it had something to do with my room.
It could be that there is just that big of a difference in the response between the two drivers, perhaps. i.e. there is nothing wrong with the driver, there is just some variation between the two. We will certainly know more when I swap in a new diaphragm later this week. Either way, it is a good idea to have an extra pair of replacement diaphragms on hand.
So that all being said, I don't think this a spontaneously acquired dip, but I will figure out what is going on. I'd love if some of the other Super V owners who have the gear to make measurements would see how close their left and right P.Audio drivers are in terms of FR. I'd be curious.