Text blasts well within the 160 character limit are being split into multiple messages, typically out of order, when they contain non-GSM characters. For example, the following text blast was received in this manner:
"This is a text message sent from NationBuilder with non-GSM characters: ó It will likely break into multiple messages. txt STOP to leave."
It looks like this is a restriction put on by our text carrier that we cannot control at the moment. We have updated our documentation to reflect this difference.
"If you are sending a text with one or more non-GSM characters, limit your text to 70 characters or less. If your text goes over 70 characters, your text will still send, but it will automatically split into separate messages of 70 characters or less."