MK 152 Failure of IC1 after a few days

Hi
I helped my son build up this kit over Christmas and all went well. I was very impressed by the quality and presentation of the kit which gives a good introduction to soldering techniques. However, after a couple of days the cycling effect of the LEDs stopped and pressing the button just caused one LED to light, usually LD1 or LD2, and then fade. Looking on a scope it was clear that one of the gates of IC1, B,C or F, was short circuit, not allowing the gates to trigger fully low, then starting the oscillator and sinking the LEDs. I swapped out IC1 and all was good. I can’t see any reason why IC1 should be stressed in this circuit so is this just ‘infant’ failure of the component?
Any comments would be helpful.
Cheers,
Tony McCormick

maybe the pads touched each other when laying on a metal surface or loose peace of wire?

Best Regards,
VEL337