Hey @gregoryncurran! Welcome to the community. 😊
Here are some things I found on the web that may help:
Make sure to enable group messaging in your iPhone’s settings. Maybe you accidentally disabled the option. If the option is already on, disable it and restart your device. Then re-enable group messaging and check the results.
Go to Settings, select Messages, and turn Group Messaging on or off. Additionally, make sure to enable MMS Messaging as well.
Check if you have non-iMessage users in your group. Your iPhone sends group messages as individual messages to non-iOS users. The reply comes back as an individual message as well.
You may also get individual replies to group messages if users disabled iMessage or Group Messaging on their devices.
Update your iPhone to the latest iOS version and check if the problem persists. If this glitch is caused by an unexpected bug in the iMessage code, chances are Apple has already fixed the problem in the latest iOS release. Go to Settings, select General and tap Software Update to check for updates.
I hope that helps!