Team,
We have many experience on aluminum discoloration, how two reason:
1. too long time material in water or dry, for example, material in tank when we fixing, operator do not remove basket from the unload location when finish wash.
2. Do not continue locate more than 4 baskets into washing machine. Because drying is the bottle neck, when machine in dry tank, the material in wash tank can not move to next tank and case long time wash.