U-verse picture freezes

About every 5 to 10 minutes our tvs (at different times) freeze. They then go to an error page, then they go back to the show or recording.  We can also fix it by changing the channel but lose so much tv time!  We are so frustrated!  This has been going on for months and is getting worse & worse.  

ATT sent us all new boxes and other equipment.  Today a tech came out and worked for three hours - reset and reinstalled everything BUT could not fix it. Don’t know what else to do!  

Any thoughts?