Driving a 74HC series chip with a 74LS series
An HC chip needs >70% Vcc for the high voltage, which an LS gate is not guaranteed to deliver.

Use a pullup resistor on the output of the LS. Its output is rated to sink 8mA, so you can go down as far as a 620ohm resistor, though a higher value will use less current in the low state. 1k is a reasonable value to try. You cannot go too high in value, otherwise the pullup speed into load capacitance will be too slow and still not fix your multiple clock transitions. You will need to experiment with this if you want to use less current.