A lot of phones(including Androids) have issues when receiving SMS and MMS, the other day we had a problem with a certification made by a carrier that failed.
Our software was getting disconnected when a MMS arrived(not even downloaded), turns out the phone connection was getting completely locked for more than 1 minute and that only happened with said carrier, with another the issue only happened when the MMS was downloaded. The whole thing is a a mess, both from manufacturers and carriers.