jms1055,
Thank you for replying back!
We understand that the message threads that are being silenced are message threads with your contacts.
To verify, for the message threads that are being silenced are these showing the crescent moon Do Not Disturb icon next to them?
If so, we’d advise checking to see if Hide Alerts is turned on for that message thread. Hide Alerts can silence incoming notifications for just an individual message thread and would be a separate setting from Do Not Disturb. We’d advise checking out the “Mute notifications for a conversation” section in this resource below for useful steps that can be used to turn Hide Alerts On/Off:
Change message notifications on iPhone
With Do Not Disturb, when this setting is turned on and the “Silence” setting is set to Always, all incoming calls and notifications will be silenced even when the device is unlocked. With the “Silence” setting set to “While iPhone is Locked”, incoming calls and notifications are silenced only while the device is locked. If you’re seeking to not silence calls or notifications, you can turn Do Not Disturb off in Settings > Do Not Disturb.
Have a great day!