For some reason, I get duplicate SMS threads for a few contacts. It's very random... I can count four contacts with duplicate threads; i.e. two identical threads for the same contact. When I text that contact, what I send will post to both threads; when they reply, it will go to both threads. If I try to remove one thread, the other thread stays but all the content in the thread disappears. So the only solution is to delete the entire conversation. I even have one thread that is tripled (three identical threads). If I try to delete one of them, the other two remain but the texts within both threads disappear.
A battery pull failed to remedy the situation.