Its too risky to buy second hand without seeing the TV in person really. The seller could be shifting it because they don't like the uniformity, for example. At very least you'd want to get some pics of some gray slides to see.
Also depends where you buy from, I'd be more inclined to trust a long-term member selling their TV here than a random seller on eBay.
The U8Q is a 2020 model and as 2022 models are released it will become 2 years old. Doubt places have enough stock at all for it to come down in price again, but I could be wrong. Usually, 2020 models have sold out by now.
If you're working with a tight budget consider a refurb instead:
To coincide with the Bargain - Panasonic refurbished eBay store thread I am also making this thread to stay as a bargain thread throughout the year. Much the same as the Panasonic thread, deals on this outlet tend to peak around this time of year (25/03/20 today) as they are trying to ship out...
www.avforums.com
Sony X900H and especially the new X90J are better alternatives than the U7Q. The U8Q is more similar to the X95J/XH9505 though.