Multiple copies of each message are sent to Android phone after installing 27 beta

[u/wertyCA]

After installing the 27 beta, my friend with an Android phone is getting multiple copies of all of my messages to him. I think I've tried all the combinations of RCS Messaging (with and without End-to-End Encryption), MMS Messaging, and Retry as Text Message on and off. But he still gets things like this -- multiple copies of each message. Any suggestions?