About three weeks into moving where we are now, I discovered water all over our basement floor as we did a late night load of towels. (Our washer empties directly into the drain in our basement floor) Other units started to complain of water, too. Once the plumber put the camera through, he discovered a blockage of feminine products and q-tips right where the property pipe joins with the city sewer pipe. At least, that's what our landlord told us. Plumber burnt out his tools trying to break it up, so they had to get RotoRooter from Osky to come down and finish it.
Not sure what happened, but I hope our landlord figured it out and evicted whoever did that.