No, i've looked at the flipper switch, there's a healthy gap there.
It's not triggered by tapping the cabinet or anything microphonic like that, it's ONLY when pressing the left-flipper button.

Also, it's not the same sound each time, there's a variety of boings/dings and even the odd explosion is triggered too.
I imagine there's a common supply rail that the flipper coil is spiking.

Thanx,
Marty