Problem formulation must follow goal formulation because;
In goal formulation, we decide which aspects we are interested in and which aspects can be ignored. In the goal formulation process, the goal is to be set and we should assess those states in which the goal is satisfied.
In problem formulation, we decide how to manipulate the important aspects, and ignore the others.
So, without doing goal formulation, if we do the problem formulation, we would not know what to include in our problem and what to leave, and what should be achieved. So problem formulation must follow goal formulation. That means problem formulation must be done only after the goal formation is done.