Sensing 230v across motor with Shelly i4 failing

[c64]

I'm attempting to use a Shelly i4 (https://kb.shelly.cloud/knowledge-base/shelly-plus-i4) to sense when 230v is applied to a water pump. Circuit A is what I am trying to implement, but no matter the position of the mechanical water pressure switch, the Shelly always reports ON.

The Shelly works as expected when I remove the motor from the circuit. ie wiring exactly as their circuit diagram suggests. When the motor is in the circuit and the switch is off there is 0v AC across the motor so I'm confused what is going on.

Does anyone have an idea of how I can make this work with the motor? Thank you.

 

[Bluejets]

Is the installation in an MEN arrangement...?
Sounds like you might have feedback voltage from the neutral line.
Some electronic "gadgets" can be susceptible to such voltage.
As a test, I'd tend to run a relay across the motor and then feed your"magic box" with a set of dead relay contacts configured however.