There is a problem in trying to use the mux as demux in the reverse direction. When it works as a mux, all the voltages in the circuit are well defined, driven by low source impedances (TOP and DOWN)., but when it works as demux, the nodes gets driven or left floating. So they hold whatever they held sometime back or what they acquired during transition.
So if you want the other outputs to be quiet, you need to expicitly drive zero volts when they are not needed. You cant expect them to behave nicely when they are floating.
You could chuck the first two TGs., tie input side of all the 4 TGs to the input and use a one-hot decoder to do the job., in addition to providing a ground path to all the outputs when not in use.