I don't know if manufacturers are using less durable metal, or if it's because of higher average yields and more acres-per-producer, but we're seeing a lot more wear to sieves than in years past.
Maybe it's because producers keep machinery longer due to poor commodity prices. Whatever the reason, it's important to carefully inspect all the components of sieves before heading to the field with a modern combine. The little rods that run crosswise through the sieve frames, on which the louvers pivot to increase or decrease sieve openings, can wear where they pass through the sieve frame pieces. It's tough to see those pivot points without removing the sieve--unless you're willing to crawl onto the sieves and use a flashlight to carefully examine those potential wear points.
Another sign of wear is if the edges of the tips of the louvers are sharp. That becomes an issue when the metal of the louvers gets so thin, leading to the louvers getting so thin they bend or won't hold position. When you consider the tons of crop residue that slides across those sieves each year, it's not surprising that they eventually become nearly as flexible as aluminum foil.
A final concern, especially with new combines that allow producers to adjust sieve openings from the cab, is if adjustment linkages get frozen from rust or crop debris, or if those linkages get out of calibration. I've seen situations where the indicator in the cab said the sieve was barely open, but in reality the louvers were standing nearly straight up. The operator couldn't figure out why he kept throwing over grain, even though "...the cab display says I've got it nearly closed."
When it comes to displays and readouts in combine cabs that are supposed to reflect actual settings or adjustments in a combine, it's best to take the advice of Ronald Reagan, who famously quoted an old Russian proverb that states, "Trust, but verify."