solution results and iterations number

Hi,

I am running time-dependent model fully copuled with termination techniques set to iteration and tolerance. I see under progress that the nonlinear solver reaches ~100% with the last iteration (that I define under maximum nuber of iterations) then moves on, and if I increase the maximum nuber of iterations I get different result. This means that the solution is not reliably , right?
what sould I do to fix this?
thanks,
Shahrazad