The thing is there is literally a section and definition of this type of product right inside of eBay. And item (properly) listed as "for parts or not working" is 100% buyer's risk. So long as you are actually shipping what is described in the listing, you (seller) are 100% in the right.
Unfortunately, due to a ton of illegal activity, eBay has become stupidly strict these days. I recently got my account moderated for selling pokemon games (because fakes exist and I didn;t have a high enough sell count in the last few months). I was selling copies of X and Y (of which fakes do not exist). It's impossible for eBay to keep tabs on every listing, so sometimes the honest person gets screwed because of dishonest people in the past.
I still think the OP has a very good chance of winning this, especially if he/she has some good feedbacks and has been around ebay longer than a couple of months. If the buyer claims he got something totally different (ie a my little pny plus rather than an iPhone), then things COULD get a little tought since it is hard to prove what was actually sent without images/video/etc.)