SMS status 'Sent' not 'Delivered' 12 hours after sending

Hiya,

Does anyone have experience with this for AU number sending SMS to AU numbers? I know it's on the carrier side if Dialpad status is in 'Sent', but we send out a weekly text campaign, and a few numbers have been stuck in the 'Sent' status the next day. Not the same customers, different numbers each time.

Is there anything we can do in our implementation to mitigate this?

Thanks