I purchased two identical items, but one arrived defective. Is there a way to initiate a return for just the defective item?

Hi all! I purchased two refurbished Acer monitors from the official Acer store. Unfortunately, one monitor arrived with a dead pixel near the center of the screen. I reached out to Acer, provided several pictures of the issue, and asked if they could process an exchange. They messaged me back saying they can offer a partial refund of $10 and that I can keep the device as is or initiate a return for a full refund.

However, I don’t see the option to return just one of the two monitors on the eBay app. The other monitor arrived in perfect condition, and I’ve already set it up, so I don’t want to go through the hassle of returning both. Plus, they’ve increased the price of the monitor, so returning both and repurchasing them isn’t the most ideal solution for me. Is there a way I could return, or preferably exchange, just one of the two monitors? So far, I’ve only communicated with them and haven’t contacted eBay or PayPal.