People return figures for all kinds of reasons. It doesn't have to be a defective figure. Some defects can be fixed. No I don't think Sideshow should discount a figure just because someone had previously returned it if the issue was corrected.
Then don't advertise the item as "new" then. There is no justifiable reason for Sideshow to sell an item that was opened, used, returned, and fixed as new. Don't want to sell those items as used? Fine, then they should take the hit financially with a warehouse full of used items they won't sell because they can't charge full price for it. This isn't a charity. When I see a product listed as "new" on Sideshow's website, I should expect a pristine item that was never opened. I shouldn't have to cross my fingers that I am actually getting what I paid for. This wouldn't be acceptable with any other retailer, so I don't understand why Sideshow should get a pass.