I just saw your thread now. And this is a real common problem.
As I sell many lasers ... I do take the chance the buyer will mess the laser or get it at a broken condition for some reason ... and then complain.
In my case I always offer a repair. Even if I know for %100 he messed the laser and killed it. As I know what PayPal will do. So I rather save money and send him a new laser or something.
It is a hard thing when you sell something personal like in your case , you are not the builder of this laser. So you thought a partial refund will do and that it is okay.
I totally understand you , and I also thank you for exposing him. What I always do just in case someone will try to trick me at the end ... I take a video of the laser working and in the video I usually say the customer name or write it on a paper. Evidence of the item working before shipment. That helps sometimes.
:beer: