grouped sonos speakers separate every morning

Sonos speakers are designed to go to a lower power state when not in use, which may be what’s affecting the group.
 

Have you tried creating them and saving as a named group rather than a dynamic one? 

Haven’t done that. Will need to search how to create a named group.

Thanks.

Settings, scroll down to Groups, then Create Group

Groups should survive a low power state.  It’s not going to survive a reboot, so if power is being cut to any/all of the units, the grouping will be lost. 

Also, if one or more of the rooms is connected to a TV, a group will be broken up when the TV input is used.  You can prevent this from happening by setting “Ungroup on Autoplay” to “Off” under the “TV Autoplay” settings. 

Thanks so much! Will try your last suggestion.

Is your router or wifi doing anything unfriendly in the middle of the night? Reboot, channel change or the like?

Any alarms set? Could they ungroup, if the ‘Include Grouped Rooms’ is not enabled on the alarm(s)?

Nothing with the router; seems that it was the use of the soundbar with the TV. I’ve now set up a named group that we can use in the future.

Thanks, everyone!