Text messages getting mixed up

[Sigma_sailor]

Today I sent a text message from my iPhone 4(iOS 6) to an iPhone 4S (IOS 5) user. He received the first part of a text I sent him some weeks ago joined to the second part of the text I sent today. Read together strangely it turned into a criticism of him which was never intended. Does anyone know if this is a sending iPhone or receiving iPhone issue?