@ja_zz
I don't know what 'off center' means, in this case, but
Do you think it was damaged in the shipping?
It was generous for the seller to accept the speakers back.
He sounds like a 'Stand Up' guy.
For me, I would send it to Mr. V. as his drivers are made to his specifications and I would doubt anyone else knows what he knows. (I also wonder if he needs the driver from the other speaker in order to get them balanced)?-Ask Johnny.
A second reason to send it back to California is that Vandersteen constantly upgrades their speakers and I am sure they would need to see your driver in its' pristine state in order to affect the proper repair. If you have it repaired locally, it may get altered so that should you still need to send it back, they might have a problem putting it back to original spec. as they don't keep records of their upgrades.(Though I wonder why they don't). Of course, I am being a bit paranoid, but I want to save you from anymore trouble.
A third reason is that should you want to sell them, you would have all the documentation showing they were put back to original by the manufacturer.
Lastly:
When In Doubt, Contact Johnny R!
Bob