The 'ping' sound is fron the string popping against small grooves in the nut as it's tightened. The grooves are caused by the force of even normal playing. I used to put a piece of string cover paper in the slot then tighten the string until it broke through the paper. Then I'd tear away the excess and the ping would disappear. Afterward when I had the time and money I'd have the slot dressed by my trusted luthier until the slot got so worn I'd have to replace the nut. Did this every couple of years when I was gigging 20-25 days out of a month.

Would venture the reason for g string breakage at the bridge has much to do with the force of one's strum. My problem was similar until I'd developed enough restraint in my attack. That plus I started letting the sound system do the work.