I have a PVC drain line for toilet on first floor--seems it was poured concrete--home built in 1930's--problem is -we removed the tile, 12'x 12' when we remodeled approximately 10 years ago--now the toilet seems to "rock" from side to side; also, every couple of days I need to "square " the toilet to the back wall. Question: is the flange bad? I did not notice screws holding the flange in place when I had removed the toilet years ago--but now we have the toilet rocking and not staying in line with the back wall. I am lost as to what to do. Thank you.