Training the operators is the -only- real answer, since there is no way that little roll pin can withstand an operators ham handed ramming of the switches lever.
I have also noticed that operators that were never trained not to jump out of the seat have a tendency to hit this lever with their knees as they egress the machine while facing away form the machine, which also causes/exacerbates this problem.
Maybe you can ask to speak to the operator it happened to to see what he was doing just before the failure, and show him the problem/ instruct him as to the proper method of changing directions.
Do you change the entire assembly or just the roll pin, since wear on the related parts may be a part of the problem?