The pump is more reliable than semi, primarily because it opens later than the semi, so fewer hot gases enter the chamber area, drying it out. Semi-autos tend to rust in the chamber, if not cleaned. More semi's jam because of that and feeding issues than pumps, but pumps require a person to pull back on the handle as the trigger is pulled, so it does a full stroke after firing.
Levers usually work pretty well, until battered rounds fail to feed and dented cases fail to extract. People who own them, never clean/lube the action, and use the same box of ammo for 30 years are the culprits. The other problem is found in older 94s, where the hammer is dropped on the half-cock notch, breaking it off.
There are also more loading errors with lever guns, especially in cold weather, when full-cocked hammers slip off gloved, young thumbs, resulting in unintentional discharge. I've witnessed a few of those.