I am having a problem transferring SMS w/ MMS messages from a Galaxy S6 to a Galaxy S8+. I've tried this with the SMS Backup & Restore app and also the Samsung Smart Switch app. I've tried to use the AT&T Mobile Transfer app but it keeps crashing. I am able to backup the messages with either app. However, when I restored, it only restores messages that I have received from other people. Messages that I had sent to the same recipients were not transferred to the new phone unless they were from several months back. It is strange because messages that I have sent recently (past month or so) have not transferred but messages that people have sent me are 100% transferred regardless of how old or new the messages are. Full disclosure, I have a lot of SMS messages from years past so perhaps this problem is that there are too many messages to restore? The backup files are about 3GB. Any ideas would be appreciated.