We have 4 phones with the same issues. We upgraded to the latest Messenger + and MMS stopped working reliably on all 4. Granted they are 2 YO Galaxy Core phones but they worked fine before the latest upgrade. I reset 3 back to a much older version and they worked OK. Upgraded again this evening and we're back to very slow response on messages - especially MMS. It just says downloading for hours. Some messages don't even make it through. Too much of a good thing causing us all issues?? I'll just switch to Googles Messenger if this doesn't get fixed soon.