"...escalated to the management and will be used to improve our production process. I'm sorry the stick fell short of your expectations." Makes it sound like you are the one "at fault", what a crock! That isn't an apology, even though they used the word "sorry" in the sentence. The proper response should be "We apologize your stick made it through our rigorous QC process and was delivered out of spec to what you ordered, we'd like to offer you a discount off your next order with us if you'd be willing to continue giving us your business".