2000 Chevy Trailerblazer Engine Shuts Off When in Brake

I have a 2000 Chevy Trailblazer with 156k miles.

Within the last month when at a stoplight or stop sign or even when I hit the
brake backing into the driveway, the car's engine will shutoff. The only way to
fix is to put the car in park and then turn the engine back on turning the key
in the ignition. The problem does not happen all the time, which is making it
frustrating and harder to diagnose.

I've been two different mechanics, both who have had the car for over a
week. Neither one had the issue happen to them while driving it. They both
checked for error codes, none appeared on the engine, gas pump, nothing.
One mech did a smoke test and found some leaks which he fixed, but the
problem still occurs.

The car run great otherwise. No check engine lights or other apparent
issues. Battery is 3 months old. Had a good tune up in last 2 months with no
major issues.

Any idea what this could be? It's my wife's primary car so I'm concerned
about her driving it since we don't know what's causing this.