When shearing a sheep, the wool items created will stutter while flying. This is not the case when shearing mooshrooms or performing other actions which create item entities.

The specific problem is that in net.minecraft.world.entity.animal.Sheep#shear, both the client and server generate random numbers for the velocities of the spawned items. This can be compared with net.minecraft.world.entity.animal.MushroomCow#shear and net.minecraft.world.entity.monster.Bogged#spawnShearedMushrooms, neither of which use locally generated random numbers on either side.