Cat D8T Engine Miss Firing

I am operating a Cat D8T here in New Zealand.
It has an engine miss firing problem, usually later in the day when fuel gets lower in the tank. No problem early in the day
We have had the Cat dealer look at it twice, but nothing shows up on their computer, making us think it may be a fuel issue. Have replaced the fuel filters early in the piece, but problem still persists.
The engine will go onto 5 cylinders, sometimes even 4, after 2 or 3 minutes it will clear itself and continue for maybe...

Cat D8T Engine Miss Firing

Cat D8T Engine Miss Firing