Signal bleed thru mechanical switcher box

[SorryGregorry]

Hello Forum Members,
My case is-as follows:
I did a 4 channel passive switcher that consist of 2 Independent switches in paralel on each channel from input to output:
-momentary
- spdt (on/off)the circuit is housed in aluminium box - all circuits share common ground via contact surface of imput/output jack.
A signal bleed between channels appears as switches remain in off position.
My goal is to keep this box passive.
I have tied to add an input buffer made of tl074- for each channel- between input pin and rest of circuit to privide a matching impedance (high on input/low on output)- same result.
Thanks in advance for your suggestions.
Cheers,
Greg

[induction]

A diagram and photos of the build would make it easier for us to help.