Match chain and ground speed to avoid bulldozing or not enough dirt and tubers on chains. Hugger belts help prevent roll back which reduces bruising, but hugger belt speed must be matched to elevator belt below or hugger belt will skin potatoes. Adjust digging blades so tubers flow onto the primary chain and not into the blade. This unseen damage of tubers being torn by digger blade can be a major source of tuber bruising. The pitch of the digger blade can greatly affect the easy flow of dirt and tubers up the primary.
Many machines have too much pitch to blades.
Avoid fast changes in tuber pulp temperature. Only use shakers when necessary. Drop deviner chain onto secondary chain to avoid back bouncing and have deviner chain act as flights at first. Look for sharp edges and cover them with belts. Use belted full width chain if possible.