My wife got 1.7 billion on my stargate a few years ago. I finally cracked it last year and just got over 1.8 billion, but all our other high scores are around the 800 million.
When we got those billion high scores the opto server on the top right ramp was not working either.
I have now had that fixed and I can't even get close to that score. I've always had it on tournament mode because thats the only way I can get free play.
I have a switch just inside the door that turns the tournament mode off and on but I use the flippers in settings to change it.
You can do a 6 quartz trade and get 50 million for that, do a few of those and it builds up quick.