Most home kitchen scales display weight in 1-gram increments, so the margin of error when measuring 2 grams of yeast can be as much as half the amount. The scale is not broken; that is its resolution. The solution is to change the method, not the scale: weigh a larger amount and divide it, or use a spoon measure for that ingredient.
Accuracy and resolution are different features of a kitchen scale, and they are often confused. Accuracy is how close the number shown by the scale is to the actual weight. Resolution is the smallest increment the scale can display. Most home scales display 1-gram increments; if the display reads 2 grams, the actual weight could be anywhere between 1.5 and 2.5 grams. The scale is not broken, and it may be properly calibrated; the limit is in the device itself, and calibration cannot remove it. That is why the precision statement on a scale’s box does not tell you the smallest amount it can measure.
This limit is not noticeable for larger measurements. When weighing 500 grams of flour, an uncertainty of 1 gram is a margin of 2 parts per thousand, and no dough will notice it. The same uncertainty in a 2-gram amount of leavener approaches half the amount. In other words, the error rate grows as the amount gets smaller, and is greatest for the most sensitive ingredients: yeast, baking powder, baking soda, and salt. Since these ingredients directly affect how dough rises and tastes, a deviation is immediately noticeable in the result. The same scale is reliable for a large amount and unreliable for a small one; the same scale measures both amounts.
The first solution is dividing, and it requires no tools. If a recipe calls for 2 grams of yeast, weigh 10 grams, divide it into five equal piles on the counter, and use one pile. With a 10-gram measurement, the 1-gram uncertainty drops to 10%; even if you divide by five by eye, the total error is smaller than it was at the start. The same method works for salt and spices. Store the remaining piles in a closed container and use them in the next batch of dough, so nothing goes to waste.
The second solution is to use a spoon, which is often more practical for small amounts. A measuring spoon measures volume and does not have a resolution problem; a tablespoon is 15, a dessert spoon 10, and a teaspoon 5 ml. The only condition when using spoons is to fill them level, because a heaping spoon holds noticeably more than a level one. Using the same spoon consistently for an ingredient maintains consistency better than a scale. Spoon measurements bypass the scale entirely, avoiding the resolution problem altogether.
The third option is to replace the scale itself, though not every kitchen needs to. Small scales that read in increments of 0.1 gram are available and can make things easier for someone who works with sourdough, develops their own blends, or mixes spices. They usually have a low capacity, so they cannot weigh 1 kilogram of flour; that means you need two scales at home. If you do not have this need, dividing and spoon-measuring are enough for everyday recipes.