Have you tried force stopping the Messages, clearing its cache and rebooting your device, as well? Since this seems to be a persisting issue, please send us an error report. We apologize for the inconvenience and appreciate your contribution to the beta program.
One UI Beta Team
On your specific Galaxy phone 2 methods (related to storing and parsing the raw PDU) are missing! Which means only apps that implement their own MMS PDU parsing would work. Chomp has always relied on the MMS methods provided in Android.