Did this excessive, and momentary (you mentioned <1 second long) jerking, which if I understand you properly only has happened once, occur while shifting out of park?
It's possible after shifting into park, if the wheels were under torque (e.g., pressed into a curb, or holding the car against a hill), and then especially if you set the emergency brake like that, and left the emergency brake set after starting the car back up the next time and taking it out of "park", that it could cause a pretty significant and sudden jerk/bang sound to get it out of park. It could also be physically difficult to get the car out of park, in this sort of situation.
Best parking practice is to avoid stressing the parking pawl by keeping the brakes (footbrake and/or emergency brakes) applied during and after putting the gear into "park", and keeping the brake applied until moving it out of "park".
https://en.m.wikipedia.org/wiki/Parking_pawl
But this sudden release of the parking pawl when under toque, if you just did it once or a few times, probably won't have damaged anything, so you don't need to worry about it if that's what happened. (But, do change your parking technique so as to not make it a habit.
).
I hope I understood your description correctly, and that's all your problem was, but if you're concerned, you might want to ask someone to check out your car who is knowledgeable. I hope you can find a better mechanic than the guy you wrote about in
this thread!
Best of luck to you!