Same paint but two shades from two buckets

Hello Sir/Madam

I have a problem with dulux paint . My house is five years old , its been painted 2 times with dulux exterior paint which is giving 10 years of garantee. All that is not a matter of a fact, your dulux paint peals off and cracks in a year time there is no quality in your product. Now im paiting again while the paint was painted two years ago.

I bought a paint for exterior which comes in 20 liters of a shade called beige sand, when I painted the two buckets I got two different shades. What could be the problem because these paint is not mixed in the shop, but it comes mixed from the manufaturer.

KS Moloko ********** 426 **********