Those are actually two different statements, and they're both untrue.
1. There are several things that can go wrong with a levergun, stemming from an inherently weaker action than most bolt-actions, and even than many semi-autos, typical use of rimmed cartridges, and operator error.
2. See the last two issues. There are extremely few autoloaders that fire revolver cartridges. It's also much easier for an operator to induce a stoppage during a stressful situation.
Now that I've told you why I believe your statements are not based in fact, I'd love to hear any actual evidence you have.
John