My toilet bangs every time it is flushed. This started to happen after a plumber changed the inside flush mechanism. He also did some type of cutting under the toilet tank to put the piece in; I am not sure what he did exactly; I was not there. His reasoning is that the flange is going. It seems odd to me that this all began after he worked on the toilet and that is his only reason. I think he did some damage. I did, however stop the banging by putting thin plastic mesh under the toilet, since now, after the plumber's work the toilet is loose. This worked until my mother took the mesh out to clean the floor. Now I cannot get it to stop banging. Additionally, every so often the toilet will not completely flush. I have to empty a bucket of water into it to make it flush completely. HELP! Do you have any advice? Do I need an entire new toilet? Thanks.