Somewhat broken 74HC00 ic. What happened to it?
The 50mA draw indicates that the chip has been damaged, and ESD is a likely cause, or trigger, for such damage. A damaged chip could exhibit strange behavior as you indicate, perhaps because of power supply bypassing that is insufficient for such a high fault current (it's possible that if you shunted the 100nF cap with 1000uF it would appear to work properly). 

To make your circuit more bulletproof, I suggest adding 10K resistors in series with the gate inputs so that any kind of ESD coming from the switch will cause less current to flow through the protection networks on the chip. Like this: 







simulate this circuit &ndash; Schematic created using CircuitLab