4066N analogue switch rapidly switching ON/OFF when should be OFF
As the 74HCT4066 is a CMOS part, the inputs are very high impedance and must be connected to something at all times.  If they are left unconnected, they will float around to random voltages - an un-connected input cannot be assumed to be a logic zero.

Connect 10K resistors between all unused logic inputs (even the ones for the sections you are not using) and Ground to ensure that the inputs are indeed "Low" when you remove your +1.64 volt input (and that is a bit low to be guaranteed to be considered a "High".)

According to the datasheet, the enable inputs should be above 2.0 volts to be certain to be recognized as "High" or logic 1, and below 0.8 volts for a "Low" or logic zero.

Also, 1.6 volts is a bit low for most red LEDs.  We normally run LEDs with a voltage somewhat higher than their rated forward voltage, with a resistor in series to limit the current to an acceptable value (which can be much less than their recommended maximum current).