How can I fix a loose In Sink Erator 333 SS-31?

I have an In Sink Erator 333 SS-31. It came with the house so I do not know how old it is. It is grinding occassionaly and very loudly when it works. I read the other posts and able to move it in either direction without problems from top and bottom (allen wrench). When I move it from the top, it wobbles and is very loose, but cannot be taken out. Is this normal? You can push it down at any angle. I try to keep it flat. The 2 bolts in the center allow the plate to be moved. Is it supposed to be this way? To be able to be moved? Do I need a plumber and/or a new unit? Please help. Do not want to spend any $$ on plumber if it is something easy to fix. Thanks in advance for any advice.