Perhaps an evil spell??

I have a Discus 2cT with about 650 hours on it. Schempp-Hirth did the
instrument installation, and a more professional looking job you will
not find. But there was one problem that confounded even the avionics
guy: when the engine was running, pressing the push-to-talk button
would kill the engine until the button was released.

The engine's ignition is a very simple magneto (Solo 2350), and the
radio a Dittel FSG2T radio, - yes, the one with a recall. How to
explain the ability of the radio to ground the magneto?? No one even
had a theory. But when I reinstalled the radio after the recall
service (which was very efficiently and courteously handled by Dittel,
BTW), the problem was gone. I tried to induce the problem several
different days, but it exists no more.

So what flaw in this radio can cause such an effect? A black curse?