Well........ I've got my first screwing as a seller on eBay after many many sales.
Buyer after 2 weeks claims item wasn't as described, THOUGH in his return request he states that the item says , used, not working and that the photos DO show the area in question as defective.
eBay says " send him a return label and get it back because if you don't we will refund him anyway and you won't have your item."
WOW. Glad the shipping cost was negligible both ways. I'm wondering what happens if I never get it back or it's not my item etc etc. Then what.
Oh well. I've been initiated into the "screwed by eBay" club.
I'm sorry to hear this

. Unfortunately it is becoming all too common on eBay these days. Sounds like maybe your buyer knows that it is as described but got buyer's remorse or whatever. Or else they took parts from it in order to repair another unit. But even if you do get the correct item back, you are paying shipping so you still lose.
If you don't get your item back or if it is missing parts, not much you can do I'm afraid.
eBay badly wants to be another Amazon and so they kind of wish that small, low volume and occasional sellers would just go away. Way more money for them to be made with high volume store style sales, car sales, etc.
Better to sell elsewhere if you can.....