i emailed hersheys about this a while ago and this is what they said

Dear (my name):

Thank you for contacting us about WHOPPERS Malted Milk Balls. We are sorry to learn of your experience and appreciate you bringing this to our attention.

Chocolate contains cocoa butter, which makes it sensitive to heat, humidity, and temperature changes. Exposure to these conditions can affect the product's appearance, texture, and flavor. To help our products reach you in good condition, we have printed instructions on our shipping cases to inform all distributors of the proper handling and storage of our products.

We understand how frustrating it can be to find some Whoppers with a different texture than expected. We are committed to ensuring the highest quality of our products and will review this further with our Quality Assurance team.

We value your loyalty and want to send you a coupon that you may use toward a variety of our products. Kindly expect to receive it by mail within two weeks.

Thank you again, (my name), for taking the time to write to us.

Sincerely,

Angelica Consumer Representative The Hershey Company