Do I need to do anything? Or can I ignore?

I sell on Vinted but only just started on eBay. I sold an item in good faith it worked perfectly well, it’s a kids’ trike. They messaged one day after transfer of funds with the below message saying it wasn’t “safe” and I hadn’t disclosed this in the listing and therefore it was within eBay terms for a return. It’s practically brand new and less than half the normal RRP.

For what’s it’s worth, we have another one we have at ours (this was at grandparents) and it took a few days to get used to how it handled. I was a bit disappointed when I first got it thinking it wasn’t a big flimsy. But. We got used to it. Loved it and used it non stop and even got a second one for grandparents house.

Is it right they can ask for a return? How would I even go about it? They would have to pay for it I assume? And then, how can I be sure they won’t just sent back a broken one or one in poor condition?