All my listings are BIN and immediate payment required, so "unpaid item" issue doesn't directly affect me. I could make the case that I shouldn't have that 'unpaid item' block in place, and I can see it has blocked six sales in the last 60 days.
OTOH, I wonder if UPI isn't a 'leading indicator' of a buyer who will otherwise be problematic. If you don't pay for what you buy, what other nonsense will you pull?
Wondering what the 'mood of the room' is on that?
Your vote: Block them