Our toilet rocks back and forth as you unseat yourself. Upon inspecting the 2 bolts that attatch the bowl to the floor (the ones with the white plastic caps over them) I found one is completely loose and I can remove it. But I can not seem to be able to realign it and tighten it up. These bolts attach to some flange correct? Could the flange be broken? Also, I will be having a heavy person using the toilet so I was wondering if stronger bolts/flanges are available (or even necessary). Much thanks for any advice someone can provide.