Multiplexer CD74HC4051, always giving a true out
Being CMOS, you need to make sure that all of the address inputs are either connected to Vcc or GND since once you charge up the gate capacitances of the decoder's input MOSFETs they'll stay charged up for a long time when the address dip switches go open-circuit.

I don't see any pull-downs on the chip side of your address dip switch, so you need to connect about 10k from each of them to GND.