Duplicates are not that uncommon in SMS. It is just an old protocol. Most apps, Pulse SMS included, will filter out duplicates on the receiving side.
If the messages are only showing up once, within Pulse SMS, then the app is only sending them a single time. Whatever is displayed in Pulse SMS is what will be sent, the app has no retry or re-send logic built in, even for messages that fail to send. If this is the case, then the duplication is happening at the carrier level.
