ATT U-verse with Giga Fiber, When TV's pixelate, internet is extremely slow

Had U-verse prior to upgrading to AT&T fiber with U-verse, but never had the pixelation or slow internet issues,

d till around November, then pixelation and internet slow downs started, but we're tolerable until about a week ago.  

It tends to happen randomly.  I have checked all wired connections, rebooted DVR, and receivers multiple times.  When issue occurs no change in light's on the ONI or Modem/Router.  No new network equipment, I have even tried disconnecting WIFI, and wired devices, but no change.  I have the 5268AC modem/Router.  Any assistance would be greatly appreciated.