My own G20 when brand new, came out of the box a total jam-o-matic. It had a bad trigger bar rubbing against the bottom of the slide so hard that it just would not move freely at all - ever. It also had some kind of coating of crap all over the extractor that looked like a coating of epoxy glue from being glued into the slot - or if it was some other accidental coating, somebody would have had to hammer the extractor into the slide instead of making sure it fit and moved freely. The extractor was stuck in place that hard, and had to be pried out of it's slot with a metal tool....
It's totally amazing how bad the quality control at the Glock factory must be to let people get away with assembling a gun so horribly incorrect. I really think a disgruntled employee deliberately sabotaged my new gun when he put it together. you couldn't possibly screw up a gun that badly by accident.