If it's a bubble magus, then make a small platform so it's not sitting on the bottom of ur sump, the water comes out through the bottom so if there's no clearance for the water coming out then it creates back pressure and causes it to overflow, I had the same exact problem and took me hours to figure it out, so basically just raise it a few inches so the the water has enough room to run out, and remember the higher the number u set it too the lower the flow, this is if it's the bubble magus