Upon arrival, Mirela (one of the two hosts) informed us that the toilet was "taking longer than usual, about 10 minutes, to flush." We confirmed that the toilet was in working order, and proceeded to check in. Later that night, we used the bathroom and it was completely blocked with poop and pee floating in an almost overflowing toilet.
We called the number provided and Marco (the other host) picked up. We explained that we did not have a working toilet (the bed is 2 meters away from the toilet too so the smell was awful). He asked us to try fixing it ourselves, then after a few exchanges, he hung up on us. We called Airbnb support and stayed up for half the night to report the situation.
The next morning, we called Marco again who seemed more apologetic after Airbnb support got in contact with him. He moved us to another unit with a working toilet, and despite Mirela previously promising a price reduction, we did not get any (Airbnb support gave us a 14 euros refund). The rest of the stay progressed normally.
Pros: location is close to attractions, price is very low, free pastry breakfast. Cons: host was unreachable/unresponsive despite an emergency, poor wifi and cellular connection, and honestly, the reeking toilet filled with human waste that's 2 metres away from our bed made our first night in Rome a nightmare. Wish the hosts were upfront about the toilet completely not working from the beginning.