Hi @NeelamB91
SMS is always tricky to debug. In your case, the fact that the SMS are sent 1 hour to each other would indicate a retry on Adobe Campaign side.
Retry will happen if Adobe does not receive the response (SUBMIT_SM_RESP) in the timely manner to the send request (SUBMIT_SM). I would say in your case, you should have no SUBMIT_SM_RESP received within the expiration time (configured on the SMPP External Account)
Check whether you have SUBMIT_SM_RESP with the same ID than the faulty SUBMIT_SM, if you've got SUBMIT_SM_RESP, check the date & time these were received and compare with the "Expiration period of the MT" in the external account. if the response is received AFTER that period, the delivery is considered a failure and retry will kick in.
I suspect this is what happens for you.
Check this great video Adapt SMS connector to your SMPP provider and the associated documentation.
Hope this helps,
Thanks
Denis