Hmm according to the datasheet 74hcxx can drive a 25mA load where hcf40xx can 10mA. So the problem does not seem to be the drive capability. I simulated the circuit and i faced the same problem. I then realized that the sytem can't start up properly. The chip that i use is a latch(74hc279). Inputs of the latch changes before the output can at the start then it becames locked. If i add a small delay to one of the inputs then it starts up and runs properly in the simulation but i didn't tried on real yet. Although this seems in simulation, the situation is interesting. Because the inputs are also depended with the output. I didn't understand how input could change without the output. Anyway i'll test the real circuit and i hope it responds well.