It caked
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Caking
The product takes up moisture and sets. It is the defining failure of the dry half of this category, and it happens in storage rather than in production.
Where the moisture comes in
An inadequate seal, a liner that did not land properly, dust on the sealing surface at filling, or a customer opening and reclosing the container in a humid building.
Dust at the fill is the one you control
Filling a dry product at speed throws dust, and dust between a liner and a rim is a seal that looks closed and is not. Wiping the rim belongs in the process rather than in the instructions.
Settling, which is not caking
The product compacts in transit and the container looks underfilled. Nothing is wrong, and customers report it as if something is, which is an argument for declaring by weight and saying so clearly.
Separation in a blend
Ingredients of different particle sizes separate when a container is shaken and carried. A premix that was homogeneous at packing can deliver a different dose from the top than the bottom.
Which is a real compliance exposure
A guaranteed analysis is a statement about the product in the container. If it segregates, a sample taken from the top may not meet the guarantee even though the batch did.
Test it the way it lives
Filled, closed, warm, humid, for weeks, then shaken and opened. Weigh it, look at the liner, and sample from the top and the bottom.
Anti-caking agents are a formulation answer, not a packaging one
They work, they are declared on the ingredient list like anything else, and they do not substitute for a seal. A product that needs both should have both rather than one standing in for the other.
Tell the customer how to store it
Cool, dry, closed, and not on a concrete floor. It costs a line on the label and it prevents the failure that generates the most complaints in this category.