Identical board (using IC MM74HC123) problem

I have two identical circuit boards using IC MM74HC123 one manufactured by Fairchild Semiconductor the other by Philips. The Fairchild chip when used in the circuit will announce any length of message the Philip circuit won't announce the longer messages. I don't have a circuit diagram for the board. I only difference in the propagation delay, output transition time and power dissipation capacitance. Could anyone please tell me which of these would course the problem and why?