Milk Clotting from vending machine

We have three vending machines which vend freshbrew, but recently w changed two and now the powdered milk is starting to clot and float i the tea - has anyone else experience this and an suggest a solution. We have had the water tested and no obvious differences. The machine are less than 6 months old and new Stentorfield Evolution machines. The ingredients do not give us problems on other machines or sites s we are stuck