We have oil leaking from the flywheel side of the Cummins KTA 19 G 3 engine on our crane. seal seams ok?

We have checked and found that the seals are ok and the seal cover O-ring also in good condition. The maker rep's attempts to stem the leak are also futileWe have oil leaking from the flywheel side of the Cummins KTA 19 G 3 engine on our crane. seal seams ok?
It is ether the rear main seal or the have a main seal housing, that goes onto the rear of the block and then the seal drives in that instead of the block and rear main. You will more than likly have to remove the flywheel to see in there, but you do not have to remove the crank on those engines.We have oil leaking from the flywheel side of the Cummins KTA 19 G 3 engine on our crane. seal seams ok?
Can you see the main seal going around the crankshaft behind the flywheel? Cause that seal is alot impossible to see the condition without dropping the crank or pulling the seal.