I think you need to find a plumber with a video cam who can check all the lines for breaks and dips etc. to be sure nothing else is wrong. Sump pump basin is a hole for outside water to drain into through a perimeter drain system and then be pumped out with a sump pump. Until you know the condition of the pipe and the source of the plugs, you are never safe. Your tenant or one of your kids could be doing something you don't know about. A plumber with a jet cutter may do a better pipe cleaning job if that is part of the problem.