sounds like it was an actual accident.
good to hear that he was willing to try and make it right.
Last Ebay purchase I made was a spindle for a lathe, what was presented and what I got were totally different, when braced with it the seller claimed -I- had swapped the spindle and was trying to rip him off, never was compensated for it. Now have two bad spindles and a serious reluctance to deal with Ebay. luckily I have two other lathes and some nice steel, so will carry through with the original plan and make a new spindle.
Most sellers WILL try to make it right, so it's always best to present a chance, presented in a civil manner it can result in a great outcome. Presented wrongly, it puts the guy in a bad mood, and a very obstinate disposition. The fact that he is willing to provide a replacement shows that he was upright on it.
Good deal I'd say!
ken.