I know this, because here's what happened.
I ordered five cables on September 4. A few weeks later, a package arrived, containing one cable. I emailed the company about it; I do understand that mistakes can be made, but mistakes can be rectified, and everyone is happy. They asked me to send them a picture, so I took a picture of the one cable that arrived, and emailed it to them. This, of course, doesn't really help them, but they asked for a picture, so I sent it.
A couple of weeks later, a package arrived with the missing four cables. So now I was happy.
Up till this point, I hadn't raised a formal Ebay dispute, because the company was fixing the problem, and I hadn't given feedback, same reason. But now I was happy, so I went to give positive feedback.
And I found that I couldn't.
The reason Ebay gave is, "Item 271903328040 was not found because: This item number does not exist. Or you've already left Feedback."
But the item does exist and I have not left feedback. And, according to my Ebay "purchase history", I didn't buy it. Except that I did, because I have the cables and the company has my money. I'm a bit baffled about this.
So if something had gone wrong, I would have been unable to raise an Ebay dispute, and this is because Ebay have a 45 day period for opening a dispute.
So here's the thing. Even if the seller is working towards fixing things, you should open a dispute within 45 days of the purchase. A dispute isn't a claim, it's just putting down a marker. You then have 20 days after that, to escalate it to a claim (or close the dispute).
In my case, it was only a few pounds worth of cables, and had a happy ending. But it's worth knowing about the time limits for future reference.